Oils are composed of base oils and additives. Typically, additives are sacrificial; they deplete first before the base oil is affected. As such, by trending their quantities over time, we can gain insight into a few of the conditions to which the oil is subjected.

By interpreting these conditions and patterns, we can correlate them with the health of the asset and plan accordingly for possible repairs or maintenance. In this article, we will do a deeper dive into ways these can be explored to add value to your asset management program.

Why Do Additives Matter?

Additives come in various ratios and chemical compositions, but when we talk about additives in oils, they really have three main functions. They can either;

• Enhance the properties of the base oil, which already exist
• Suppress the undesirable base oil properties or
• Impart new properties to the base oil

On their own, they cannot affect anything, but when coupled with a base oil, they can impact an asset. Base oils also have specific properties, which, when combined with additives, allow assets to perform at their best.

The real performance comes from how the additives and base oil work together.

As shown in Figure 1, some additives that enhance properties include antioxidants, corrosion inhibitors, anti-foam agents, and demulsifying agents. Those responsible for suppressing undesirable properties can include pour-point depressants and viscosity improvers.

Finally, those responsible for imparting new properties include extreme-pressure additives, detergents, metal deactivators, and tackiness agents.

Here are some quick descriptions for a few of these additives, which will help you to gain an appreciation of their functions:

Antioxidants: these protect the oil from oxidation. They are very common in Turbine oils but can be found in many other oils. They are the first line of defense when oxidation begins and react with free radicals to neutralize them before they attack the base oil. 

Corrosion inhibitors: adsorb onto the metal surfaces to help protect them. Comprised of sodium sulphonates, alkylbenzene sulphonates, or alkylphosphoric acid partial esters.

Anti-foam agents: reduce surface tension to break up foam formation. Typically, these are silicon-based, although silicone-free defoamers also exist.

Demulsifying agents: enable water and oil to separate. These were formerly composed of barium and calcium, but modern formulations use special polyethylene glycols.

Pour point depressant: alters oil crystallization, allowing the oil to form fewer crystals at lower temperatures.   

Viscosity improvers: specifically designed to ensure that the viscosity of the lubricant can be more tolerant of changes in temperature and shear.  

Extreme pressure additives: used under high stress to prevent the welding of moving parts. Usually comprised of a phosphorus compound.

Antiwear additives: designed to reduce wear under moderate stress. The most famous sulphur-phosphorus compound is ZDDP (Zinc Dialkyl dithiophosphate).

Detergents: keep oil soluble combustion products in suspension (especially for engine oils) and ensure they do not agglomerate. These usually contain metal additives such as Calcium and Magnesium.   

Understanding the function and composition of these additives can help us to determine how they are performing in the oil. Since many of these are sacrificial, their values will decrease over time. As such, it is important to trend these values to determine whether they are remaining constant, increasing, decreasing, or decreasing at an accelerated rate.

How Can Additives Deplete?

Additives can be depleted through different mechanisms. Some of these include:

• Regular consumption through normal functioning of the lubricant
• Antioxidant depletion during oxidation
• Antiwear depletion due to high wear on the inside of the equipment
• Additive depletion via a contaminant to produce a bleaching effect

As mentioned earlier, additives are sacrificial in nature. It is very normal to see additives deplete over time; if they are not depleting and increasing, this may be a cause for concern. This can mean that someone is topping up the oil frequently or perhaps topping up with an incorrect lubricant.

Since there are numerous oils on the market, the best way to monitor the depletion of your additives is to compare them against a new sample of that oil and use that as your baseline. Your lab will help you confirm when the additive limits are approaching the danger zones.

During oxidation, a free radical is formed under conditions such as heat, wear, metal catalysts, oxygen, or water. These free radicals are unstable, and antioxidants usually neutralize them.

In the process, antioxidant levels decrease. However, if the conditions still permit oxidation, more free radicals will be formed. This means that more antioxidants will be depleted as they neutralize the free radicals until they diminish and can no longer protect the base oil. This is when the free radicals begin to attack the base oil, and varnish can form.  

Once the antioxidants are gone, the oil stops defending – and starts degrading.

If there are causes of high wear, such as the incorrect viscosity of the lubricant (too thin) or the machine finishing of the inner parts of a component not being done to the required standard, this can affect the levels of antiwear in the oil. Antiwear additives protect the metal surfaces inside the equipment. However, these are only activated when moderate stress exists within the equipment.

Typically, in these situations, the antiwear additive adheres to the metal surface and helps protect it by forming a layer. Once this layer is formed, the antiwear additive has officially left the oil, and this will be reflected in a decrease in its value in the oil analysis report.

The layer will not remain forever, and due to wear on the equipment, it can be worn off and replaced by a new layer, leading to further depletion of the antiwear additives until there are no more to form another layer or protect the metal surface.

Contamination can also cause some additives to become depleted. Contaminants can react with additives, causing them to form deposits that leave the oil. Therefore, their presence will not be detected by oil analysis.

Some common contaminants are water, fuel, coolant, and acids. These contaminants can also promote the formation of catalysts for degradation mechanisms such as oxidation. Dirt and solid particles can also promote additive depletion, especially when they act as catalysts. 

What Tools Can Be Used to Monitor Additive Depletion?

There are some basic analytical tools that can be used to measure the quantity of additives in oils. The spectroscopy methods are the FTIR (Fourier Transform Infrared) and ICP (Inductively Coupled Plasma). Another method is the RULER® test exclusively designed for antioxidants.

With FTIR and ICP methods, users obtain quantitative values for the elements present in the tested oil sample. These are usually reported in ppm and trended over time. Figure 2 shows an extract from a Turbine Sample report from Eurofins lab, where the levels of additives (and contaminants) are shown. When trending this, analysts should pay attention to the rate at which these additives decrease and whether an increase or decrease is noticed.

Another tool that can be used is the RULER® (Remaining Useful Life Evaluation Routine) test, which specifically quantifies the levels of antioxidants remaining in the oil. It trends the values, compares them against the baseline for that oil, and then determines the change as a percentage.

If the RULER value falls below 25%, the antioxidant levels have reached a critical level, and one may consider replacing the oil. 

Figure 3 shows a RULER graph, which identifies the presence of different types of antioxidants (Amines) and antiwear additives (ZDDP), as well as oxidation products (Fluitec, 2022).

This is a comprehensive readout of the quantities of these additive types at the time of sampling. It is easy to get a quick snapshot of its trend over time and determine whether it is declining rapidly or reaching critical levels.

The key to using these analytical tools is to provide insight into what is happening inside the equipment, allowing us to determine whether any preventive action is needed.

By monitoring the quantities of these additives over time, we can easily establish whether oxidation is occurring, which can lead to varnish and overheating of the asset. We can also determine whether significant wear is occurring as the antiwear additives are depleted (confirmed by the presence of wear metals in the oil analysis). When monitoring your asset’s health, trending specific additive levels can also be very useful. 

References

Eurofins. (2025, September 06). Annual Turbine Analysis. Retrieved from Eurofins Testoil: https://testoil.com/services/turbine-oil-analysis/annual-turbine-analysis/

Fluitec. (2022, September 29). Why is LSV Used for RULER Analysis? Retrieved from Fluitec: https://www.fluitec.com/2022/09/29/why-is-lsv-used-for-ruler-analysis/

Sometimes we can spend hours poring over technical data sheets, comparing oil performances, and finally selecting the “right” oil which aligns with the needs of our equipment. Then, within 2 months, the oil degrades, our machines shut down, and we have a bunch of maintenance repairs lined up. What went wrong? We clearly had the “right” oil in the equipment; everything should have worked beautifully. This is where the awareness of lubrication and its practices becomes critical.

Having the correct oil is only one part of the puzzle. Being able to deliver that oil in its purest, cleanest form to the machine is often one of the other pieces that go missing. Another piece is selecting the right oil, not just based on the sales guy’s advice, but on the actual operating conditions of your machine. In this article, we dive a bit deeper into ways you can align the right oil with the proper practices, or avoid the wrong ones, to help extend the life of your asset.

Spec Sheet vs Strategy

For this example, we will consider a turbine oil selection. If a customer wants to change the oil in their turbine, then they may consider the following:

• What are the OEM specifications that need to be met?
• Is this oil available from the local supplier?
• How does it compare to other oils on the market?
• Does the cost justify the value? (or will the purchasing department want something cheaper?

For most of these questions, engineers or the person tasked with selecting the oil can readily find the answers in the oil’s technical data sheet and by talking to their sales representative. But if we dive a bit deeper, are we selecting the right oil for the operating and environmental conditions? Let’s examine the selection of a turbine oil for the Siemens SGT 200 Gas turbine that meets the Siemens TLV 9013 04 specification.

As seen in this document from Shell Lubricants, a few of their products meet that specification, namely Shell Turbo T, Turbo S2GX, Turbo S4X & Turbo S4GX.

On the other hand, Mobil provides some solutions as well, namely, Mobil DTE 732, 746, or DTE 832, 846

Chevron also provides an option of Chevron GST as follows:

With so many options, how can one choose the “right” oil? They all meet the required Siemens specification, TLV 9013 04. This is where the data sheets, OEM manual, and knowledge of the equipment’s operating conditions play a crucial role.

As per the manual, there are preset conditions for temperatures and pressures, but if your actual system runs hotter (or production is being pushed a bit more), it is functioning outside the operating envelope.

The spec sheet tells you what the oil can do. Your operating conditions tell you what it must do.

Additionally, if your surroundings are harsh (close to the sea or in a corrosive environment, or in a non-ventilated area where heat can build up), these can place additional stress on the equipment. For these harsher conditions, a synthetic oil might be more appropriate than a mineral oil, albeit more expensive in terms of the initial investment.

The manual also specifies which tests/characteristics should be used to monitor the condition of the oil, namely: viscosity, particle count, water content, demulsibility, air release, foaming characteristics, RULER®, and MPC. Based on the performance of your current oil in the system, you can determine whether these values fluctuate toward the higher warning zones. This can also influence your decision about which oil to choose.

It’s not just about the right oil or one that aligns with OEM requirements. The selection should also be based on the environmental conditions of the oil and the equipment, and on whether the oil is suited to perform in these conditions. A mineral oil will not withstand the temperatures that a synthetic oil can for extended periods without degrading. Similarly, given the “right” conditions, synthetic oils can also degrade. By cross-examining your spec sheet, OEM manual, and actual conditions, you can determine the best-suited oil for your operations.

Common Modes of Failure

Regardless of the oil selected, common modes of failure can occur with every lubricant. These include: contamination, improper storage and handling practices, and environmental factors, as shown in Figure 4.

Contamination can be defined as any foreign particle entering the system. This includes any gases, liquids, or solids. Especially when the lubricant system runs alongside the process side, process gases and liquids can leak into the oil. These contaminants can influence the oil’s degradation, leading to deposits or chemical reactions that break it down. Common process contaminants include ammonia or treated water.

 The biggest threat to the right oil is often what gets added to it – whether it’s process contamination or the wrong oil during a top-up.

Another liquid that can contaminate oil is another oil. During top-ups, operators can add the wrong oil to the system, causing contamination and, depending on the oil, a possible shutdown. Adding motor oil to hydraulic oil can be catastrophic, as the additive packages work differently and the motor oil additives may counteract the hydraulic additives, removing them from the oil, leaving the asset open to wear and failure. Despite selecting the correct lubricant for your system, adding the wrong oil (mistakenly) will shorten its lifecycle and cause the asset to fail. 

Bad storage and handling practices can also erode your oil, regardless of the oil you choose. Turbine and hydraulic oils are used in precise equipment. As such, they need to be clean and free of dirt or other contaminants. However, if oils are not stored correctly, contaminants can enter and contaminate the oil.

Simple techniques, such as transferring oil from larger storage containers (pails, drums, or totes) into smaller, more manageable containers (2-3 liters or less), can introduce contaminants into the oil if not done correctly. If oils are to be transferred to another storage container, the storage container must be clean. The transfer process should use clean hoses (not previously used for another lubricant) and be completed in a dust-free environment.

If you wouldn’t use a dirty needle for a blood transfusion, why would you use a dirty hose for an oil transfer?

The transfer of oils from one container to the next can be thought of as a blood transfusion. Would you use dirty needles or vials to transport the blood to be placed into another human? Similarly, oil can be likened to the equipment’s lifeblood and should be treated accordingly. Just as we observe sterile practices for blood transfusions, we should also observe similar types of practices for oil transfers.

Environmental and operational factors can also influence lubricant degradation. As stated earlier, all lubricants can degrade over time under harsh conditions. The lubricant formulation largely influences this, as does whether it was blended to withstand those conditions.

Oxidation can easily occur when temperatures increase, free radicals are present, or when wear metals are present. Thermal degradation occurs when the temperatures exceed 200°C. On the other hand, microdieseling occurs in the presence of entrained air, despite the lubricant used in the system, as shown in Figure 5.

Any of these degradation mechanisms can occur regardless of the type of oil chosen. Hence, it is essential to remember that operational conditions and environmental factors can heavily influence oil degradation, even when the oil is appropriate for the system.

Role of Condition Monitoring

As mentioned earlier, choosing the right oil for the system is just one part of the puzzle. How do we know the oil is performing when it’s in the system? This is where condition monitoring can work hand in hand to help ensure that the oil does not fail the asset.

If a proper oil analysis program does not exist, operators will not know whether the oil is properly lubricating the asset. They will also not be aware of whether the oil is breaking down too quickly and failing to protect the asset. Oil analysis can also alert operators to signs of wear in the asset, so they can fix them before they turn into functional failures.

An oil analysis program that lives in a drawer protects assets about as well as no program at all.

There is also the possibility that an oil analysis program exists but is not top of mind, or that its results are put in a drawer. This can also cause the asset to fail even though the correct oil is being used. Apart from the aforementioned factors, if operators are not warned of the impending failure of the oil, this can result in production losses, increased downtime, and, in some extreme cases, the complete loss of the asset if it has failed beyond repair. 

Incorrect sampling is another area in which the actual condition of the asset is not reported. Even with the correct oil used, if a sample is collected from a dead leg or an area that is not truly representative of the conditions inside the component, its actual condition will not be known. With incorrect data about the component, the asset can be misdiagnosed or treated for symptoms that do not exist, which can lead to its detriment.

Human and Organizational Factors

Not all failures occur at the equipment level; human and organizational factors can also cause the asset to fail even when the correct oil is used. If humans aren’t properly trained in oil sampling techniques or storage and handling practices, these can affect the asset’s functionality. We often forget that, at the heart of it all, lies the human factor, which is partially governed by the organization’s systems.

Training needs are an organizational factor that is often overlooked when considering how an asset can fail. However, if operators have not been trained in condition monitoring techniques, they will not be able to read oil analysis reports or take appropriate actions to protect the asset. Training can help bridge some competency gaps that directly impact asset performance.

It doesn’t matter what oil is in the system if no one is trained to monitor it – or motivated to care.

Culture is another factor swept under the rug. If the culture doesn’t exist to look after the assets, it doesn’t matter what type of oil is placed in the system; the asset will fail eventually. The performance of the asset does not only rely on using the correct oil. By implementing a culture of Asset ownership, where operators look after the asset and are accountable for its performance, assets are optimized to provide the functionality they should. This is one way to ensure the right oil is used to enable the assets’ performance.

Another area of concern is the documentation of maintenance procedures. If maintenance procedures are not adequately documented, someone new to the operation may not be aware of the correct practice. This, coupled with a lack of training, can spell disaster for the equipment. In these cases, even though the right oil was selected, the wrong practice or lack thereof can fail the asset.

Turning the “Right oil” into the “Right Outcome.”

As explained in this article, improper practices can jeopardize the asset’s health, even when the right oil is used. However, if all the right things align, we can have an asset that lasts for its expected lifetime or beyond.

This starts with selecting the right oil based on the application, environmental conditions, and OEM recommendations. If we follow this up with good storage and handling practices, proper condition-monitoring programs, documentation, and training, we can look toward a longer-lasting asset. The right oil enables reliability – but only disciplined practices deliver it.

Compressors are integral to many of our operations. They are used to compress gas, increasing its pressure, and to power tools. They can also be used as vacuum pumps or blowers, but each application is different. As such, they require various types of lubrication, particularly for applications that use specific refrigerants and come into contact with the lubricant.

In all these applications, the functions of the oil remain largely the same: it must lubricate the surfaces, prevent wear and corrosion, maintain the required viscosity, and provide proper sealing.

In this article, we will dive into the various types of compressor oils and explain why they are suited to these applications. We will also discuss monitoring the health of these oils and the tests that should be performed to ensure your compressor oils remain healthy.

Types of Compressors

Essentially, there are two main types of compressors: Displacement and Dynamic. For displacement compressors, gas is drawn into a chamber, compressed, and expelled by a reciprocating piston. On the other hand, for dynamic compressors, turbine wheels accelerate a medium, which is then abruptly accelerated.¹

Positive displacement compressors include Reciprocating and Rotating compressors. These can be further subdivided as shown in Figure 1. For Dynamic (Turbo) compressors, these are further subdivided into Centrifugal, Axial, and Mixed types (also shown in Figure 1).

Depending on the type of compressor, the required lubricant will vary. For example, positive-displacement compressors use rolling or sliding motion and include bearing and sealing components within the compression chamber. On the other hand, dynamic compressors use hydrodynamic journal and thrust bearings, or rolling-element bearings, to support the main shaft, which is isolated from the compression chamber.

Working pressures, temperatures, and the type of gas being compressed also play a significant role in determining the appropriate lubricant.²

As with most applications, there can be a dry-sump or a wet-sump. Wet sumps are typically seen in reciprocating and rotary screw compressors.  In a wet sump, the gas usually contacts the oil, lowering its viscosity. This is where it is essential to note the gas’s solubility in the system oil. Natural gas and other hydrocarbons are more soluble in mineral oils and PAOs than in PAGs and diesters. Thus, PAGs may be preferred in some cases to avoid lubricant failure.

Compressor Oils

Most of the major global lubricant OEMs have classified their oils based on:

• Rotary vane and screw air compressor oils
• Reciprocating (piston) air compressor oils
• Refrigeration compressor oils

As seen below in Figure 2, Shell Lubricants³ has a line of lubricants, particularly for air compressors, which are further classified into mineral oils, PAOs, and PAGs for Rotary vane and screw air compressors or Reciprocating (piston) air compressors.

In reciprocating air compressors, cylinder design dictates the lubrication type, as this is the most severe application. Compressing the gas usually results in high temperatures, which can easily lead to oxidation. The compressed gas must be free of contaminants, as contaminants can accelerate oxidation. Typically, for reciprocating air compressors, mineral oils or PAO- or di-ester-based lubricants in the ISO VG 68 to 150 range are preferred.

Rotary vane compressors can experience pressure extremes as the vanes slide to compress the gas, and oil is continuously injected into the compressor chambers. Typically, ISO VG 68-150 oils are used in this application.

For screw compressors, the oil must perform several functions, including lubricating the meshing rotors and the plain and roller bearings that form part of the geared coupling. ISO VG 46 mineral oils are usually used in these compressors, but the viscosity can be increased to ISO VG 68 or to synthetic PAO or PAG lubricants at higher ambient temperatures. Similarly, Group III base oils of these viscosities can be used in this area. Most screw compressor oils contain mild EP/AW performance additives and require an FZG failure load≥10.

Ideally, reciprocating piston compressors will use higher viscosities (ISO VG 100-150) with extremely low carbon residue and no or mild EP/AW additives. Conversely, screw compressors will use lower viscosities (ISO VG 46 or 68) with excellent oxidation stability and mild/high AW/EP additives1, as shown in Figure 3.

Other Industry Standards

Some other classifications which users may see when dealing with compressor oils (even though some of these standards may be dated) include:

ISO 6743-3, which uses the following acronyms for associated compressors:

• DAA, DAB, DAG to DAJ: Air compressors
• DVA to DVF: Vacuum pumps
• DGA to DGE: Gas compressors
• DRA to DRG: Refrigeration compressors

In this standard, the “D” family includes detailed classifications of lubricants used in air, gas, and refrigeration compressors. The second letter usually indicates the type of compressor, and the third letter indicates the application severity or type, especially for gas or refrigeration compressors.

For instance;

DAJ represents:

D -> Compressor Lubricant

A -> Air compressor

J-> Lubricant drain cycles of >4000 hours

DVB represents:

D-> Compressor Lubricant

V->Vacuum pumps, Positive Displacement Vacuum pumps with oil lubricated compression chambers, Reciprocating and rotary drip feed, Rotary oil-flooded (vane and screw)

B-> Low vacuum for aggressive gas (10² to10^-1kPa or 10³ to 1 mbar)

DGD represents:

D-> Compressor Lubricant

G-> Positive displacement reciprocating and rotary compressors for all gases, Compressors for refrigeration circuits or heat pump circuits, together with air compressors, are excluded.

D-> Gases that react chemically with mineral oil, usually synthetic fluids, HCI, CI2, O2, and oxygen-enriched air at all pressures. CO₂ at pressures above 10³ kPa (10 bar) with O2- and oxygen-enriched air: mineral oils are prohibited, and very few synthetic fluids are compatible.

DRB represents:

D-> Compressor Lubricant

R-> Compressors, refrigeration systems

B-> Ammonia (NH3), Miscible, Polyalkylene glycol, Commercial and industrial refrigeration, For direct expansion evaporators; PAGs for open compressors and factory-built units.

Another standard which is also used in this industry is DIN 51506, which defines:

• VB, VC: Uninhibited mineral oils (no oxidation inhibitors)
• VBL: Mineral oil-based engine oil (additives that protect from corrosion and oxidation and air compressor temperatures up to 140°C)
• VCL: Mineral oil-based engine oil (additives that protect from corrosion and oxidation and air compressor temperatures up to 160°C)
• VDL: Inhibited oils with increased aging resistance (additives that protect from corrosion and oxidation and air compressor temperatures up to 220°C, recommended for compressors with 2-stage compression)

One more standard is DIN 52503, which has these classifications:

• KAA: Not miscible with ammonia
• KAB: Miscible with ammonia
• KB: For carbon dioxide (CO2)
• KC: For partly and fully halogenated fluorinated and chlorinated hydrocarbons (CFC, HCFC)
• KD: For partly and fully fluorinated hydrocarbons (HFC, FC)
• KE: For hydrocarbons (e.g., propane, isobutane)

These standards are referenced when discussing certain compressor oils, and their definitions are helpful for navigating acronyms.

Refrigeration Lubricants

For industrial refrigeration systems, there are a couple of essential pieces of information to consider before selecting the most suitable oil. The user must know the refrigerant in use, the evaporator type (dry or wet; carryover < 15%), the evaporator temperature, the compressor type, and the outlet temperature.⁴

The refrigerant fluids are classified as per the ASHRAE classification (ANSI-ASHRAE Standard 34-2001):

• R717 — Ammonia
• R12 — Chlorofluorocarbon (CFC)
• R22 — Hydrochlorofluorocarbon (HCFC)
• R600a — Isobutane
• R744 — Carbon dioxide (CO2)
• R134a, R404a, R507 — Hydrofluorocarbons (HFC)

It should be noted that CFCs were banned under the Montreal Protocol (1989) due to their Ozone Depletion Potential, and HCFCs are being phased out due to their Global Warming Potential.

Chevron provides some general guidelines for selecting the appropriate refrigerant, as shown in the table below.⁵

(But you should always follow the guidelines of your OEM when selecting the appropriate lubricant.)

ExxonMobil classifies its refrigeration lubricants based on refrigerant type, evaporator temperature, and compressor type (Piston, Screw, or Centrifugal). This is very helpful when determining the best-suited lubricant for your refrigerant compressor: 

PDF

Critical Condition Monitoring Tests for Compressor Oils

To ensure these oils remain healthy (and not contaminated or degraded), a few basic tests can be performed on all compressors, regardless of type (reciprocating, screw, refrigerant, etc.). These include:

• Viscosity – this is key as some of the gases can easily affect the viscosity, which (if decreased) will not provide adequate separation for the interacting surfaces and cause wear. Generally, a ±10% limit is used (though OEMs may use different values).
• Acid Number – if this begins increasing, then we have an accumulation of acids in the oil, which can be because of contamination. For most compressors, a 0.2 mg KOH/g increase is the warning limit, but for refrigeration compressors, the limit is tighter at +0.1 mg KOH/g. Always check with your OEM for these limits.
• Water content – changes by OEM and refrigerant type, as the different gases will have varied tolerances.
• Wear metals – these values will vary as per OEM, as well, since they are all designed with different types of metals. Users should look for trends or significant increases in these values to indicate wear.

Some specialty tests for compressors include:

• MPC (Membrane Patch Colorimetry) – this helps to measure if there is any potential for the oil to form varnish. Given the high temperatures these types of equipment endure and the potential for contamination, the oil is at risk of forming varnish. While limits will vary by OEM, some general guidelines to follow are 0-20 Normal, 20-30 Warning, >30 Action required
• RULER® (Remaining Useful Life Evaluation Routine) – this quantifies the remaining level of antioxidants in the oil. When oxidation occurs, the antioxidants get depleted. As such, by monitoring antioxidant levels, one can easily determine whether oxidation is happening in the oil. The general rule of thumb is that if the level falls below 25%, there are not enough antioxidants to keep the oil healthy and prevent degradation.  
• Air Release (DIN ISO 9120) – measures the ability of the oil to allow air to escape and not keep the air in the oil. If air bubbles remain in the oil, this can be devastating, as it can lead to micropitting, cavitation, or increased oxidation. Users can trend the values; if they increase, it indicates that the air is taking longer to be released, which means it is staying in the oil and in the system longer.
• Particle Count – this can identify if there are any contaminants in the system. These oils must be kept clean, and OEMs typically specify target cleanliness levels.

Compressors are critical equipment, and we must understand how they work and the lubricant specifications required. Monitoring their health can also help us avoid unnecessary downtime and keep our facilities running.   

References

1. Mang, T., & Dresel, W. (2007). Lubricants and Lubrication. Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA.
2. Totten, G. E. (2006). Handbook of Lubrication and Tribology – Volume 1 Application and Maintenance – Second Edition. Boca Raton: CRC Press.
3. Shell Lubricants. (2025, November 08). The Shell Corena range. Retrieved from Shell Lubricants Compressor Oils: https://www.shell.com/business-customers/lubricants-for-business/products/shell-corena-compressor-oils/_jcr_content/root/main/containersection-0/simple_1354779491/promo_1484925192/links/item0.stream/1759302155345/17be2a9a74057f321bb209128933f68f8b88ca70/s
4. ExxonMobil. (2025, November 08). Refrigeration Lubricant Selection for Industrial Systems. Retrieved from ExxonMobil Lubricants: https://www.mobil.com/lubricants/-/media/project/wep/mobil/mobil-row-us-1/new-pdf/refrigeration-lubricant-selection-for-industrial-systems.pdf
5. Chevron Lubricants. (2025, November 08). Optimizing compressor performance and equipment life through best lubrication practices Chevron. Retrieved from Chevron Lubricants: https://www.chevronlubricants.com/content/dam/external/industrial/en_us/sales-material/all-other/Whitepaper_CompressorOils.pdf

Understanding Electrostatic Spark Discharge and Its Impact on Lubrication Systems

Electrostatic Spark Discharge typically occurs when static is built up in an oil at a molecular level, causing it to discharge in the system and create free radicals, which increase the opportunity for varnish to form. This usually occurs at temperatures of around 10,000 °C.

If we were to liken this to an everyday situation, we could think about walking around a carpeted room where the static builds up in our body. When we touch a metallic object (more than likely a door handle), we get a bit of a shock as the built-up static is discharged through us and the door handle.

Inside a lubricant system, static doesn’t just build – it ignites microscopic sparks powerful enough to scar filters and start the chain reaction that leads to varnish.

Similarly, in lubricants, static exists at a molecular level, and in areas of tighter clearances, some molecules are forced to rub against each other, causing a buildup of static. When it accumulates to the point of becoming a full charge, it dissipates at the first opportunity, usually at the filter membrane or some sharp-edged object along the way. These are seen as burnt patches on the filter membrane.

When this spark occurs, it creates a chemical reaction that generates free radicals. Free radicals are highly reactive species that need to engage with other substances. These are the initiators of varnish, and their presence can accelerate reactions, leading to deposits forming in the lubricant. Eventually, this will lead to a system that has experienced both ESD and oxidation.

In this article, we will discuss various identification methods and ways to prevent ESD in modern lubrication systems. We will also spend some time identifying typical root causes for ESD by developing a logic tree as a guide for future investigations.

How to Identify Electrostatic Spark Discharge in Lubrication Systems

Every degradation mechanism produces varying results in the form of deposits or in how these are formed. For ESD, some tell-tale signs alert the user to its occurrence. These include:

• Crackling sounds / buzzing outside of components – This noise is representative of sparks as they discharge on part of the media/asset. Typically, this occurs when the fluid is in motion, allowing it to be heard near the filters when the system is operating.  
• Burnt or pinhole filter membrane – The filters usually feel the full effect of ESD, and small burn patches or even pinholes are created when ESD occurs. When changing filters, the membranes should be examined for these patches to determine if ESD is occurring.

Free radicals are produced when ESD occurs. As such, this leads to polymerization of the lubricant, which produces varnish and sludge. This is part of the oxidation process, and the antioxidant levels will begin to decrease. During ESD, certain gases are also released in the oil. Some of the lab tests which can be used for identifying where ESD has occurred include:

• RULER® – Remaining Useful Life Evaluation Routine test, which quantifies the presence of antioxidants in the oil. By trending this over time, one will be able to determine whether the levels of antioxidants are decreasing or not. Typically, this test can be performed twice annually on larger sumps (such as turbines) or the frequency can be increased according to the criticality of the equipment. If the value gets below 25% then this is the critical limit, and methods to regenerate the oil or change it should be explored.
• MPC – Membrane Patch Colorimetry – this measures the potential of the oil to form varnish or deposits. Depending on the equipment, the warning limits will vary, but a good rule of thumb is to treat results below 10 as normal, those above 15 as within the monitor range, and those above 20-25 as the critical range. Be sure to double-check these levels with the OEM of the equipment.
• FTIR – Fourier Transform Infrared Spectroscopy can identify various molecules in the oil. It is likened to identifying the fingerprint of the oil, where each molecule has a specific characteristic spectra representative of that molecule. This test can be used to identify the presence of oxidation or any deposits that may have formed.
• DGA – Dissolved Gas Analysis – this test can be used to identify the presence of particular gases that are released during ESD, such as acetylene, ethylene, and methane.

Those above are just some of the methods that can be used to identify the presence of ESD in a lubrication system.

Effective Strategies to Prevent ESD in Lubrication

ESD occurs when there is a buildup of static in the oil; therefore, one of the best methods of preventing it is to ensure that the static levels remain low or are dissipated before they have a chance to wreak havoc on the system. The simplest and most common way of reducing this static is the installation of antistatic filters. These filters can help to remove static from the system before it builds up to dangerous levels, where it can burn the membranes or develop varnish.

Static in oil is inevitable – how you control and discharge it determines whether your system runs clean or burns itself from within.

Ensuring that the system is grounded correctly is another way to guarantee that any built-up static is removed. This is where your electricians can perform checks and install proper grounding devices for your equipment to safeguard against this buildup of static in the system. Therefore, if static charges get built up in the system, they can be dissipated without the effects of ESD.

If oils experience high levels of conductivity, they can conduct static. Typically, if the conductivity is above 100pS/m, there is potential for the fluid to conduct the charge and allow it to be discharged along the system without causing harm.

Unfortunately, there are base oils with low conductivity (below 100pS/m) that cannot carry the charge and dissipate more easily. As such, these types of oils will see an increase in the presence of ESD if not formulated correctly for modern lubrication systems.

As the viscosity of the oil decreases, more force is required to pass through the filters, which can lead to a buildup of static at a molecular level. Additionally, as temperatures decrease, the viscosity also decreases. In these cases, keeping the oil at the system temperature (designed for that particular viscosity) can help to reduce the buildup of static charge in the oil.     

Identifying the Root Causes

Thus far, all the prevention methods have focused on the physical roots of ESD. We did not explore some of the human or systemic roots that are also accountable for ESD. In this section, we will develop a logic tree designed to address a critical failure occurring in a plant. This will be used as an example of the logic tree, which can be developed when investigating the root causes of ESD.

Let’s start with the top of the logic tree, where we define the event or the reason we care. In this situation, it is an unplanned shutdown for 4 hours. An unplanned shutdown will impact the plant’s production, which is why we care about conducting this investigation.

We will assume that the failure mode occurred on one of the critical pumps, and we are investigating how that failure could have happened. Note, we did not ask the question “Why?” because it can be misleading to an opinion, and we are trying to stay as factual as possible.

A disciplined root cause analysis doesn’t start with ‘why’ – it starts with evidence. Each degradation mechanism tells its own story, and Electrostatic Spark Discharge is just one of them.

For this investigation, we will investigate the hypothesis of a critical bearing failing due to lubricant degradation. Since we are focused on ESD for this article, we will have only one hypothesis regarding the degradation mode being ESD. However, in the real world, if this logic tree were being developed, we would be investigating the six various lubricant degradation mechanisms: oxidation, thermal degradation, microdieseling, ESD, additive depletion, and contamination.

As shown in Figure 1, at the top of the logic tree, we start by placing our hypotheses on the tree, and then using evidence/facts, we can rule them out afterwards. This is a critical step as the investigation should be able to stand on its own in the court of law (even if it may not reach that point). The next hypothesis is the buildup of static in the oil. There are three possible ways for this to occur;

• Clearances too tight (as discussed earlier, this can lead to molecular friction, which can induce static)
• Less than adequate grounding system (if a proper grounding system doesn’t exist, then there isn’t an option for the static to dissipate)
• Less than adequate conductivity of the oil (if the conductivity of the oil is too low, then the charge can build up and cause it to be dissipated along the system, such as the filters)

Now, we need to investigate each of the three main hypotheses stated and find out the root causes for them.

Let’s begin with the Clearances being too tight hypothesis.

For this hypothesis, we will ask the question, “How can clearances be too tight?”. In this case (and we will have to keep it general and in broad buckets, so we can drill down into these later and eliminate as necessary), there are three possible reasons:

• The OEM could have designed the system such that it was less than adequate (LTA)
• The flow rate could have been increased above the recommended threshold
• Incorrect viscosity of the lubricant could cause additional friction (we will dive into this one later).

We will develop the other two hypotheses in Figure 2. 

If we further investigate where the OEM did not design the system effectively, we can determine that the operating conditions were probably not adequately considered before implementation. This is a systemic root cause and one that needs to be addressed with the OEM.

On the other hand, if we investigated the flow rate, there could be two main reasons for the adjustment. One could be because of system changes, which forced adjustments to the flow rate. Since a decision was made here, it is a human root cause. Someone decided to change the flow rate based on the variables involved. However, if we investigate why these changes were made (once a human is involved, the question moves from how to why), we can determine that the system was not designed to accommodate these changes. This is a systemic root. 

Similarly, if the operational conditions change (such as when a higher output is required, which is different from system changes), then the flow rate must be adjusted. Again, a decision must be made here, and a human is involved. Then we ask the question, “Why?”. In this case, we have the same systemic root, and the design is inadequate to accommodate the necessary changes.

For this part of the tree, we have found some human root causes where decisions were made, as well as systemic root causes. Both need to be addressed when we perform the final root cause analysis. For the human root causes, we can think about the procedures that guided them to make those decisions (if they existed) and amend these accordingly. 

On to the next hypothesis, which we have yet to investigate (still under the clearances being too tight), the incorrect viscosity of the lubricant, which is shown in Figure 3. There are a couple of ways in which this can happen:

• OEM recommendations were not followed
• There was an unavailability of the specified viscosity of the lubricant
• There was a less-than-adequate procedure for selecting the correct viscosity of lubricant

If we investigate why the OEM recommendations were not followed, we can find two main reasons. Either they were not documented and therefore could not be followed, or the internal best practice was used instead to replace the OEM recommendations. In both cases, these would be systemic root causes, and we should investigate why these were not documented or why they were replaced.

When investigating the unavailability of the specified viscosity of the lubricant, we can find two main causes. Either there was an issue with the restocking of this lubricant at the warehouse due to their forecasting, or appropriate checks were not carried out. This is a systemic root cause that should be investigated further.

Another hypothesis could be that the specified lubricant was unavailable from the supplier. This is another systemic root cause and should be addressed with the supplier to ensure it is resolved in the future. 

When lubricant viscosity errors trace back to missing stock or missing training, the problem isn’t the person or the product – it’s the system that allowed both to fail.

On the other hand, if we examine the procedure for selecting the correct viscosity of the lubricant, we identify a human root cause, as someone would have made the decision on which viscosity to use. But in this case, we need to investigate why the person was not trained to determine this value.

There are two main reasons why a person does not receive training: either it doesn’t exist, or it was not followed. In both cases, these are systemic roots that need to be further investigated and addressed.

Now, we will investigate the next major hypothesis, “LTA grounding of the system” in Figure 4.

When investigating the grounding of a system, we can identify two major classes: either it doesn’t exist, or it didn’t meet the requirements. If grounding did not exist, then this is an inadequate system design and therefore a systemic root cause. On the other hand, if the grounding did not meet the OEM requirements, we need to determine how this was possible.

There are two possibilities: the site’s best practices were used to replace the OEM standards, which is something we often see, especially if these requirements have worked in the past. This is a systemic root cause that should be investigated. Or there were fewer than adequate components to achieve grounding.

In this case, we can have components that are not designed for the system (do not meet the system’s requirements) or components that were not OEM-recommended and are being used (such as aftermarket products that do not meet the necessary specifications).

Finally, on to the last major hypothesis, “LTA conductivity of the oil,” as shown in Figure 5.

Figure 5: Investigation of the hypothesis, “LTA Conductivity of oil”

As noted earlier, if an oil has a conductivity of more than 100pS/m, it will be able to dissipate any accumulated charge easily. However, if it falls below this value, the charge will be dissipated in the system at the earliest opportunity.

How can oil have less than adequate conductivity? Perhaps the elements of the oil have a less-than-adequate conductivity. If that is the case, then there can be two plausible reasons for this. Either the formulation was not appropriately designed, or the materials (base oils, additives) were not of a particular standard. Both causes are systemic root causes and should be investigated further to determine if anything can be done to correct these. 

If we were to summarize a list of the root causes, we would see that many are systemic, while a few are human, as shown in Figure 6.

This further reiterates the need to develop a comprehensive logic tree when investigating any failure, as many root causes are not physical or surface-level. If these are not adequately addressed, the failure mode will recur in the future. The entire logic tree can be found here under additional support material, along with logic trees for other degradation mechanisms.

References

Mathura, S. (2020). Lubrication Degradation Mechanisms: A Complete Guide. Boca Raton: CRC Press.

Mathura, S., & Latino, R. (2021). Lubrication Degradation: Getting into the Root Causes. Boca Raton: CRC Press.

What is Condition Monitoring and Why Is It Important?

In this age of artificial Intelligence and sensors that pop on and off, we often forget about the basics and where things all started. Condition monitoring began as a way to detect anomalies in our equipment using various types of technologies. These include: vibration, ultrasound, infrared, oil analysis, and even temperature.

These were all conditions that were “aligned” with what was happening on the inside of the machine. As such, changes in their values usually indicated that something was occurring, but it was up to the trained analyst to determine if that was a good thing or a bad thing.

The most effective reliability programs blend multiple condition monitoring technologies to catch failures before they happen.

For this article, we will focus heavily on oil analysis, but this does not mean that it’s the only technology that should be used for monitoring your equipment. It has been proven that a combination of technologies can maximize the opportunity to detect an impending failure earlier and allow the maintenance team to act/plan accordingly. This can save millions of dollars depending on the industry and the type of equipment.

Using Oil Analysis as a Core Condition Monitoring Tool

Stated, oil analysis can be any test performed on the oil that has been in use in the system. It is essential to note that the oil sampled should be representative of the system; otherwise, the results can lead to operators making inaccurate decisions.

For instance, oil taken from a dead leg of the equipment or in a stagnant zone does not truly represent the oil in the system. This can give a false representation of the system and cause misdiagnosis.

Depending on the equipment being monitored, specific tests would be required to determine the health of those systems. For example, with a turbine oil, one specific test would be the RULER® test to determine the remaining useful life (in the form of antioxidants).

However, if this test were performed for a transformer oil, it would not provide the operator with the necessary information, and more aligned tests such as Viscosity, Dissolved Gas Analysis, or Flash point would be more suitable.

Benefits of Extending Oil Drain Intervals

Before diving further into the condition monitoring aspect, we need to answer the question, “Are there any real benefits to extending the oil drain interval of a piece of equipment?” The answer depends on the criticality of the equipment and the cost associated with its downtime.

Financial Gains from Extended Oil Drain Intervals

For critical equipment where maintenance downtime hampers production or availability, extending oil drain intervals offers tremendous financial benefits. For every oil drain interval, there are associated costs such as manual labor, cost of supplies (filters, new charge of oil), and disposal of used oil, to name just a few.  

Every unnecessary oil change wastes labor, materials, and money that could be invested in reliability.

Depending on the size of the sump, costs can escalate, particularly if cleaning is required before the new oil charge is placed into the equipment. Different types of applications will advise the draining of the sump and refilling with new oil, while others recommend that the sump be flushed or manually cleaned before the new oil is administered.

Additionally, if the used oil becomes heavily contaminated during use, the sump and entire system would need to be cleaned thoroughly before new oil is used.  

Safety and Environmental Advantages of Extending Oil Drain Intervals

Apart from the financial benefit of extending the oil drain interval, there are also safety and environmental benefits. If these pieces of equipment are in high-risk areas, then the humans involved in changing the oil would be placed at risk during these times.

If the oil drain interval is extended, then the humans performing these operations will have reduced hours spent in these high-risk areas. As such, it will limit the number of risk-hours and possibly lower the LTI (Loss Time Injuries) or occurrence of any such safety incidents.

Fewer oil changes mean fewer hours in hazardous zones – and fewer chances for accidents.

Every time the oil is drained from the sump, it must be disposed of safely. Typically, worksites have a dedicated area in which the used oil is stored until it is collected by a disposal provider. Some providers may charge based on the volume they collect or the frequency at which they service their customers. However, the oil must still be disposed. With longer oil drain intervals, there is a reduced volume of used oil collected by these suppliers.

Additionally, longer oil drain intervals also impact the consumption of new oil for these systems. Therefore, equipment owners would likely see a decline in the volumes of oil purchased. This also translates to a saving on the environment as resources used to create new oil are also now reduced, or rather, the demand may be reduced overall.

Another benefit of extended oil drain intervals is that the equipment is available for a longer time. This can become critical in some jobs where the equipment is needed 24/7 or even for an emergency. The availability of equipment can also translate into the potential saving of a life (depending on the equipment).

Overall, there are financial, safety, and environmental benefits to extending the oil drain interval for equipment.  

Dangers of Pushing the Limits with Oil Drain Intervals

There is always a danger in pushing limits; that’s why limits exist. They serve as guardrails to ensure that things remain within the standard envelope. As it applies to oil analysis, there are some dangers if the limits are not addressed.

Typically, maintenance intervals are determined by the number of hours worked or the mileage of equipment. These guidelines were developed by OEMs (Original Equipment Manufacturers) based on lab and, in some cases, field tests. Usually, these limits are set with some tolerance for “marginal error,” where the oil may not be changed exactly at the specified interval. However, nobody states what those margins are or what tolerance limits can be used.

In these cases, the oil, whether it has reached the end of its useful life or not, is changed in an attempt to protect the equipment from failing in the future. Hence, OEMs always recommend staying within the limits, as those are what they can guarantee / warranty. Pushing the limits may mean getting in a bit of trouble with your OEM, and they may void your warranty. However, if the benefits outweigh their concerns, then it may be time to push those limits.

What Should be Tracked in Oil Analysis

Every type of equipment will have different tests that should be performed to monitor its health. We will break down a few common types and the associated basic and some specific oil analysis tests that should be performed.

Diesel/Gasoline Engines (can be further broken down into on-road, stationary, aviation, landfill, and marine)

Basic (monthly tests)

Gearboxes (can be broken down into industrial or automotive)

Hydraulics

Turbines and Compressors

We did not dive into Electrical oils, heat transfer oil, circulating oils, metalworking fluids, or seal oils, but these will have similar type tests and some special tests as well.

Setting Up Baselines

Global oil suppliers have baseline or tolerance limits that are used when providing guidelines to customers about their equipment. The limits for a gearbox will differ from those of an engine. For instance, an iron content level of 3000ppm is normal for an automatic transmission gearbox but highly irregular for a diesel engine! Hence, it is important to know the limits associated with the application.

Some labs have also developed their own set of limits based on years of collecting hundreds of samples and liaising with their customers in the field. OEMs have also developed their own sets of limits (usually displayed in their manuals) based on their testing in the lab and on the field.

Knowing your own “normal” is more valuable than any generic industry limit.

Ideally, when developing your target levels, you should trend your data and find out what “normal” looks like for your equipment. In some cases, what is normal for your environment may be abnormal in a different environment. But it is important to note when normal varies from standard operating tolerances. This is where you would want to work together with your oil supplier, lab, and OEM to develop tolerances that align with your equipment.

Depending on your maintenance program, you can also adjust the tolerance accordingly. If you are aware that maintenance may not act on a threshold limit right away, it may be a good idea to add some padding to those limits. This ensures that the equipment does not suffer by pushing it to the limits.

Setting Oil Analysis Limits for Diesel Fleets

Let’s explore how to set the limits for a diesel engine fleet of trucks.

First, let’s categorize the trucks into critical, semi-critical, and non-critical.

The critical ones are those that, if they break down, there is no replacement; the downtime hurts us financially and can delay the project. These need to be available 24/7.

The semi-critical ones are those that still have an impact on the operation if they break down, but it’s not quite as disastrous. These can be trucks that are not on tight deadlines, can afford to have some leniency or delays with their workload.

The non-critical trucks are those that can be easily swapped out for another truck without causing any delay or impact to the project, but they are still important.

Now that these are categorized, we need to find out what types of engines are being used and what the recommended diesel engine oils are for these units. Typically, most operators have mixed fleets. Thus, one may see a wide age/mileage gap in the engines. This gives us an idea of the reliability of the engines, which can impact the setting of the tolerance limits.

Since it’s a diesel engine fleet, it would be worthwhile to consider the type of fuel being used for this fleet. With diesel engines, there are varying levels of sulphur in the fuel, which can impact the oil drain intervals as well.

For this fleet, we may need to establish varying oil drain intervals to ensure maximum reliability, based on the categories outlined by their criticality. Before adopting set oil drain intervals, it is important to execute a pilot project with the fleet to anticipate any rollout challenges for the future. We will discuss these in more detail in the case study section.

Real-World Results from a Diesel Fleet Oil Analysis Program

Fleet: Mixed long-haul trucks of various ages/mileages

Predominant oil: Mineral 15w40 Diesel engine oil (CI4 spec)

Regular Oil Drain Interval: 3000km (based on best practice over time)

Approach: An engine asset list was first compiled for every truck in the fleet. This follows the table below:

It’s important to have a column for comments as this can capture some data that we may not be aware of, such as a recent engine overhaul done to the unit, or the driver has regularly lost power over the past few weeks, or the driver tops up the oil every time he gets back to the yard.

These little details may not be captured in the CMMS (if one exists) or the maintenance logs, but they are crucial in determining whether we can safely extend the oil drain intervals or not. For units that require special attention or are under warranty, these may have to be excluded until more favorable conditions exist.

Based on the fleet (15 trucks), they were categorized into three main groups:

Critical – these units were being used every day on projects that had tight deadlines. They were often unavailable to return to the yard for maintenance or oil changes, as each hour away from the job affected the project deadline.

Semi-critical – these units were utilized by various customers at distant locations and often spent most of their time at the customer site (due to the distance). Hence, basic maintenance was usually performed at the customer’s site, causing minimal disruption to the operation.

Non-Critical – these units are often deployed in situations where extra assistance is required, or they are the standby units if one of the critical units is in trouble. 

Even though they had these three groupings, the engine types and mileages were very varied. Hence, a matrix was formed for this fleet.

The majority of the fleet falls within the 20-100,000km range, spanning across the critical, semi-critical, and non-critical categories.

A pilot test was done on the following:

• 3 of the critical units within the 20-100,000km range
• 1 semi-critical unit in the >100,000km range
• 1 non-critical unit in the > 100,000km range

Since the typical oil drain interval was 3,000km, we took samples at 1500, 2000, 2500, and then again at 3000km. Based on the trend observed from the first 3 samples, we had a fair indication of the condition of the oil before it got to 3000km.

None of the samples showed any unusual signs of wear, excessive additive depletion, or ingress of contaminants. For these samples, we kept a close eye on maintaining the following parameters:

Samples were then taken at 3500, 4000, 4500, 5000, 5500 & 6000km. Then, another set of samples was taken at 6500, 7000, 7500, and 8000km once the oil analysis values were still within range. The aim was to at least double the oil drain interval for this fleet.

Intervals of 500km were used as a cautionary value to allow enough time for any anomalies to be caught. The critical engines got to these values faster than the semi-critical and non-critical units.

All of the critical units easily got to 9000km without any of the oil analysis values entering the warning zones. However, the semi-critical unit, which had exceeded 100,000km, only made it to 8,500 km before the TBN and fuel dilution values entered the warning zone. The non-critical unit, which exceeded 100,000km, also reached 9,000 km without any issues.

Since the owner wanted to be on the side of caution (and allow some wiggle room between the intervals for trucks which could not get maintenance done at the specified interval), they chose to change the oils across the fleet at the 7500km mark but keep the oil analysis program where they perform samples at 4000 & 7000km.

They will now work alongside oil analysis, and for some trucks, where they believe they can have an even longer interval, they will extend it accordingly. 

What does this mean?

These engines take approximately 44 quarts or roughly 42 liters of oil and are changed every 3000km or roughly 2 months (critical units) with an average of 3 hours downtime for the oil change.

Hence, one unit undergoes approximately six oil changes per year:

• An average of about 3 hours x 6 times = 18 hours downtime
• An average of 42 liters x 6 times = 252 liters changed per year
• Thus, for six critical units that would be:
• Downtime => 18 hours x 6 units = 108 hours
• Oil consumption = 252 liters x 6 units = 1,512 liters

The new oil drain interval of 7500km resulted in a 2.5-fold increase in the interval.

This means that the new interval would be every 5 months instead of every 2 months.

Thus, these six units would only do oil changes twice for the year.

New downtime = 3 hours x 2 times/year x 6 units = 36 hours / year

New oil consumption = 42 liters x 2 times/year x 6 units = 504 liters

The following table summarizes the changes.

This is just for part of the fleet, and a dollar value has not been assigned to these, but clearly, there are lots of benefits to extending the oil drain interval through guided oil analysis.

Sensors vs Traditional Oil Analysis

In this age of AI, it seems that everyone is moving towards sensors and online data. Oil analysis sensors aren’t far behind in this revolution. There are mid-infrared sensors that have been engineered to relate their findings to those of regular oil tests (developed by Spectrolytic). While sensors are the way of the future, the fundamental concept remains the same. What are we doing with the data, and what data are we trending?

Sensors deliver speed, but proven lab methods still set the benchmark for accuracy.

Traditional oil analysis labs trend data, albeit the frequency of the data points is not as high as that of an online sensor. Hence, subtle/instant changes may not be readily noticed or detected. The methods used in these labs have been tried and tested over the years (and approved by various standards committees) to reflect conditions that the oil is facing in the field.

On the other hand, in the sensor world, not many of them (with the few exceptions) correlate exactly to what is being seen in the field. Hence, some lab tests, especially for the specialty tests such as RULER, MPC, and TOST (mainly for turbines), still need to be done by the lab. This is a great opportunity for traditional labs and sensor companies to collaborate and provide customers with collated data.

Moving Towards Sustainable Maintenance

While this article explicitly discusses extending the oil drain intervals for your assets, it underscores the importance of working alongside maintenance and condition monitoring to achieve these results. There is no clear cookie-cutter routine to achieve this, as each fleet of assets will be different and require varying levels of complexity for analysis. One thing is clear, though: we need to move towards sustainable maintenance.

Performing maintenance in the traditional way of just waiting for the appointed interval may be costing us increased labor and parts. However, by working alongside maintenance and condition monitoring, we can get more value from our assets and even increase our ROIs. Sustainable maintenance is the way forward for most asset owners as we move into a new era of maintenance.  

Hydraulic systems are used to transmit force from one point to another via a fluid. This fluid is usually hydraulic oil, and the concept is based on Pascal’s law. Hydraulics are present in nearly all industries and play a critical role in enhancing operational efficiency. In this article, we will take a deep dive into hydraulic oils and explore them in more detail. 

What is Hydraulic Oil?

One of the primary functions of hydraulic oil is to transmit power or energy. However, this is not its only function. Some of its primary functions include:

• Transferring pressure and motion energy
• Transferring forces and moments when used as a lubricant
• Minimization of wear to sliding surfaces under boundary friction conditions
• Minimization of friction
• Protection of components against corrosion (ferrous and non-ferrous metals)
• Dissipation of heat
• Suitability for a wide range of temperatures, good viscosity-temperature behavior
• Prolonging the life of machinery

However, hydraulic oils also have secondary and tertiary functions.

Some of the secondary characteristics of hydraulic oils include high aging stability, good thermal stability, inertness to materials, compatibility with metals and elastomers, good air separation, low foaming, good filterability, good water release, good shear stability (in the case of non-Newtonian fluids), and more.

On the other hand, some of the tertiary characteristics include low evaporation due to low vapor pressure, toxicologically harmless, ecologically safe, and low flammability (fire resistance), all of which depend on how the fluid is formulated. 

History of Hydraulic Oil

The principle of hydraulics has been around for a very long time. In fact, according to Hard Chrome Specialists, it may even date back to around 6000 BC, when ancient Mesopotamians and Egyptians used water for irrigation. Fast forward to the modern day, where hydraulics have been heavily influenced by Blaise Pascal, Joseph Bramah, Daniel Bernoulli, and William George Armstrong. A snapshot is shown in Figure 1 below.

Figure 1. History of Hydraulics as per Hard Chrome Specialists

Importance of Hydraulic Oil

Hydraulics forms part of the field of fluid technology, which can be further subdivided into hydrostatics and hydrodynamics.

For hydrostatic systems, the transfer of energy requires static pressure; hence, the pressure is high, but the flow rate is low. Fluids designed for these applications are known as hydraulic oils.

For hydrodynamic systems, the kinetic energy of the flowing fluid is utilized, resulting in low pressure but high flow rates. Fluids designed for these applications are known as power transmission oils.

As explained earlier, Pascal’s law forms the basis of hydraulics. Using the principle of the hydrostatic displacement machine, Pascal’s Law states that, “Pressure applied anywhere to a body of fluid causes a force to be transmitted equally in all directions. The force acts at right angles to any surface within or in contact with the fluid”.

Hydraulic systems utilize hydraulic oils to transmit power or energy to other applications, making them the second most crucial group of oils, after engine oils, due to their widespread use. As a result of their primary application, they can help save energy, reduce maintenance intervals and wear, increase machine life, and overall provide users with significant savings.

Types of Hydraulic Oil

There are many types of hydraulic oils due to the number of applications in which hydraulics are used. Generally, they can be classified as shown in Figure 2 below.

As can be seen above, there isn’t just one type of hydraulic oil. Depending on the application, different standards are associated with each type. The two main groups are hydrostatic applications and hydrodynamic/hydrokinetic applications.

The hydrodynamic applications mainly include ATFs (Automatic Transmission Fluids).

On the other hand, for the hydrostatic applications, the mobile systems refer to UTTO (Universal Tractor Transmission Oil) and STUO (Super Tractor Universal Oil).

These hydrostatic applications can be further categorized into mineral oil-based hydraulic fluids, fire-resistant hydraulic fluids, environmentally acceptable hydraulic fluids, and food-grade lubricants. Each of these has its associated standards and regulations.

For Mineral oil-based hydraulic fluids, there are different classifications, as shown in Figure 3 below.

For fire-resistant oils, their classifications include those shown in Figure 4 below.

For Environmentally Acceptable lubricants (particularly water-free, rapidly biodegradable hydraulic fluids), their classifications are shown in Figure 5 below.

For food-grade lubricants, their classifications include:

• NSF H1 – These are colorless, odorless, tasteless, non-toxic, and are certified for incidental contact with food
• NSF H2 – These are lubricants that can be used in food processing, but only where there is no contact with food.

(Other categories of NSF grades exist, but these do not apply directly to hydraulic oils.)

Chemical Composition of Hydraulic Oil

Due to the unique nature of hydraulic oils, they are formulated differently from other oils. Typically, it follows the regular oil formulation of Base oil + additive to give the finished product. However, many various combinations occur depending on the application for which it is being formulated.

Base Oils Used in Hydraulic Oil

Similar to other oils, any base oil can be used to create hydraulic oils. However, depending on the application in which it is being used, the type of base oil will differ. The following table gives a summary of the types of base oils used for various hydraulic oils.

Additives in Hydraulic Oil

Generally, hydraulic oils are composed of 95-98% base oil and roughly 2-5% additives. One major distinction of hydraulic oils is that they can be either zinc-containing or zinc-free (also known as ashless). The ZnDTP molecule is responsible for antiwear properties, but this does not mean that zinc-free oils do not contain some form of antiwear additive.

Zinc-free oils are formulated with no zinc and minimal concentrations of phosphorus and sulphur. These zinc-free oils are formulated for special applications where the presence of zinc could react negatively with the environment, such as equipment containing mixed metals or silver.

There are other additives used for hydraulic oils, which are classified as either surface-active additives or base-oil-active additives.  

Surface-active additives include steel/iron corrosion inhibitors, rust inhibitors, metal deactivators, wear inhibitors, friction modifiers, and detergents or dispersants.

Base active additives include: antioxidants, defoamers, VI Improvers, and pour point improvers.

Common Contaminants in Hydraulic Oil

Hydraulic systems are known for very tight clearances. As such, any form of physical contaminant can easily clog the valves or lines, leading to system failure. Keeping hydraulic oils clean is of paramount importance. Figure 6 illustrates typical clearances for hydraulic components, as well as the film thickness for various components.

The contaminants that exist in hydraulic systems can be either internally generated or externally consumed. Typically, dirt from external sources or metal wear (internally generated) form the major contaminants for hydraulic oils.

However, they are also susceptible to gaseous or liquid contaminants that can enter the system through system processes or external factors during oil handling before it enters the system. Figure 7 shows some cleanliness categories for various components.

Testing and Analyzing Hydraulic Oil Composition

There are several basic tests that should be used to determine the condition and health of hydraulic oils. These include:

• Viscosity (ASTM D445) – Generally, if this value falls below or above10-15%, there is cause for concern. Any increase in viscosity (outside of the system limits) can lead to the system experiencing higher pressures. Conversely, any decrease in viscosity outside of the limits will not allow for the full transfer of power through the fluid.
• Water content (ASTM D6304) – Too much water in a system is always a bad thing (except in a swimming pool). In particular, if the water content starts trending upwards of 500 ppm, the source of water ingression should be found and eliminated at once. This can hinder the transmission of power in the system, making it less efficient.
• Presence of wear metals (ASTM D5185-05) – These values will differ depending on the system in which the hydraulic oil is being operated. It would be a good idea to contact the OEM about the limits for the wear metals for your system to ensure that no irregular wear is occurring. The presence of these wear metals may also act as catalysts for other reactions, potentially leading to the degradation of the oil.
• Particle Count (ISO 4406) – This also depends on your system, as varying levels of cleanliness are typically aligned with different systems. However, with hydraulic systems, there is usually some guidance on the tolerance levels. The presence of these particles can hamper the transmission of power in the system or block clearances.

Specialty tests for hydraulic oils also exist. These include tests for monitoring antiwear and extreme pressure, foaming, or oxidation stability characteristics of the oil. For determining the antiwear or extreme pressure properties, tests such as the Vickers Vane pump test, 4 Ball test, and FZG rating test can be used.

Properties and Characteristics of Hydraulic Oil
Hydraulic oils must be able to withstand particular conditions and still perform their primary function of transferring power from one point to another.  As such, they have characteristics that make them unique from regular oils.

Viscosity of Hydraulic Oil

The viscosity of an oil is one of the most essential characteristics, especially for hydraulic oils, as they must transfer power. As such, the viscosity-temperature characteristic of hydraulic oils is also critical. As the temperature of the oil increases, its viscosity decreases (or becomes thinner). Similarly, if the temperature of the oil decreases, its viscosity will increase (or become thicker).

For hydraulic oils, some manufacturers plot their viscosity against temperature to help customers determine the ideal viscosity for their system based on the system’s operational temperatures. Figure 8 shows a chart for Shell Tellus S2MX, illustrating the varying viscosities as the temperature changes.

Choosing the wrong viscosity can cripple power transmission before the system even starts.

For instance, if the system is running at 60°C and the oil needs to have a viscosity of 30cSt, then an ISO VG 68 would be the most ideal oil. However, if the system is running at 40°C, and the viscosity needs to be 30cSt, then an ISO 46 oil would be more appropriate.

The relationship between viscosity and temperature is known as the viscosity index. For hydraulic oils, the higher the viscosity index, the less susceptible the viscosity is to changes in temperature. As a reference, mineral base oils have a natural viscosity index (VI) of 95-100, while synthetic ester-based base oils have a VI of 140-180, and polyglycols have a natural VI of 180-200.

Oxidation and Thermal Stability

The TOST (Turbine Oil Oxidation Stability Test) is usually used to determine the oxidation stability of an oil. Although the test name mentions “turbines”, it can also be applied to hydraulic oils.

Another test that can be used to evaluate whether oxidation has taken place or not would be the RULER® test, which quantifies the remaining antioxidants in the oil. Overall, determining the oxidation and thermal stability of the oil provides the user with an average estimate of the oil’s life expectancy when subjected to environmental extremes.

Foam and Air Release Properties

Due to the operating environment of hydraulic oils, air tends to become trapped in them. This can become a problem as it can easily lead to cavitation inside pumps (the most prevalent form of wear for these systems). Therefore, hydraulic oils must have good air release and anti-foaming properties.

Good air release allows the dissolved or trapped air to coagulate and rise to the surface, where it can then be dissipated. This is where the issue of foam “arises” as it further impedes the oil’s ability to form a full wedge between the two surfaces in any system.

Demulsibility and Water Content

Demulsibility refers to the ability of oil to repel water. Typically, hydraulic oils are designed to operate in environments with some water or high humidity, where water can easily enter the oil.

For hydraulic oils containing detergents or dispersants (DD), fluids (such as water) or other fine contaminants are usually held in suspension. Therefore, the demulsibility test, in which water and oil are mixed and then allowed to separate, will not be effective in determining the water separation characteristic of these hydraulic oils. Filtration should be used for these DD oils, which become contaminated with water.

Water in hydraulic oil isn’t harmless — it’s a silent trigger for failure.

On the other hand, for those oils that do not contain detergents or dispersants, the demulsibility test (ASTM D1401) can be performed. For this test, equal parts of oil and water are mixed at a specific temperature to create an emulsion and then allowed to separate. The amount of oil, water, and emulsion is recorded at 5-minute intervals.

If the viscosity of the oil is less than 90 cSt and there is 3 mL of emulsion or less after 30 minutes, the oil is acceptable. If the oil has a viscosity greater than 90cSt, the result is taken at the end of 60 minutes (if the value of the emulsion is less than 3 mL, it is acceptable). The results are usually recorded in the format: mL oil / mL water / mL emulsion (time recorded in minutes).

Corrosion Protection

Many hydraulic systems contain copper metals, brass, or bronze, especially in cooling systems, pumps, bearing elements, or guides. Therefore, hydraulic oils must be resistant to copper corrosion, as this could compromise the entire system. One such test, which can be used to identify the corrosivity of these oils, is the Copper Strip Corrosion test.

In this test, the copper strip is placed in hydraulic oil for a typical duration of 3 hours at 100°C. The results can be quantified based on the level of discoloration, which correlates with the degree of corrosion.

A similar type of test can also be done with steel / ferrous corrosion. In this case, the oil is mixed with distilled water or artificial seawater and stirred constantly for 24 hours at 60°C while the steel rod is submerged in the mixture.  Afterwards, the steel rod is examined for corrosion and allocated ratings accordingly.

Maintenance and Testing of Hydraulic Oil

Keeping hydraulic oils clean is critical to their operation, as any contaminant can interfere with the amount of power that they can transmit. These oils are also subjected to harsh conditions, so monitoring their quality will help to ensure that they provide the maximum efficiency for the system in which they are working.

Importance of Regular Maintenance

Hydraulic oil systems are notoriously known for leaks. Sometimes this revolves around failed seals or the improper use of material for the actual system, which cannot tolerate the existing conditions. Despite the root cause of the leak, it is essential to perform regular inspections on hydraulic equipment, as a leak can lead to a loss of power, potentially delaying or causing work in progress to come to an unexpected halt.

Hydraulic leaks are also detrimental to the environment, particularly if they seep into the ground or waterways. Hence, it is crucial to perform regular checks and maintenance on hydraulic systems to prevent harm to the environment.

A single unnoticed hydraulic leak can halt production and harm the environment.

Some other factors to consider regarding the maintenance of hydraulic fluids include maintaining the temperature and oil levels at the expected system values, as well as keeping the hydraulic oil clean to avoid contaminants.

Users should also be performing routine oil analysis (to catch any changes to the oil, which may lead to detrimental effects). Additionally, routine inspections can include checking noise levels, shock loads, filtration, vibration, leakage, fluid odor, color, and the presence of foaming. These additional methods can prove beneficial for intercepting early failures.

Common Methods for Monitoring Hydraulic Oil Condition

When monitoring hydraulic oils, several key characteristics to pay attention to include viscosity, AN (Acid Number), Water content, the presence of wear metals, and contaminants.

Any change in viscosity can affect the transfer of power, while an increase in Acid Number (AN) can indicate the degradation of the oil. On the other hand, the presence of any contaminant can also impact the performance of the oil, possibly leading to its degradation while acting as a catalyst.

Alternatively, the presence of wear metals can also indicate that wear is occurring on the inside of the hydraulic equipment. It may initiate a physical maintenance check to determine the extent of the wear.

Steps for Changing Hydraulic Oil

When changing hydraulic oil, it is important to note the previous condition of the oil. If there is a high concentration of contaminants, the system should ideally be flushed before introducing a new batch of oil. This prevents the new oil from also becoming contaminated and degrading at an accelerated rate.

Additionally, some physical contaminants may have also become lodged in the tighter clearances. Hence, it is always a good idea to perform a flush on the system, ensuring that it is clean before a new batch of oil is used.

Proper Storage and Handling

Hydraulic oils must be clean, and depending on the system, they have very specific cleanliness requirements. As such, when storing hydraulic oils, special care should be taken to ensure that the rooms are clean, the decanting equipment is clean (free from dirt or other contaminants), and a filter cart is used when decanting new oil into a system. Hydraulic oils do not mix well with other oils, and dedicated systems or equipment are required for decanting these oils.

Troubleshooting Common Issues

One of the main issues with hydraulic oils is their susceptibility to contamination. Contaminants can be in the form of physical particles, liquids, or gases.

In the case of gases, this usually leads to cavitation (one very common challenge with hydraulic oils) or an increase in the presence of foam. Hydraulic oils can also become contaminated with water, which affects their ability to transfer the required amount of power.

If your pump sounds like marbles, air or cavitation is already stealing performance.

Typically, technicians have reported hearing the “sound of marbles” within pumps that are experiencing cavitation. In these cases, there is usually an air leak or air entering the system where it is not intended to. This can be an issue with the intake or suction part of the pump, where the oil levels are low enough to allow for air to enter the system and then become trapped. In these cases, a baffle plate can be placed inside the reservoir at a 60-degree angle to trap some of the air bubbles.

On the other hand, when water is present in the hydraulic oils, depending on the concentration, a vacuum dehydrator or regular filtration system can be used to help remove the water.  Subsequently, for hydraulic oils that contain a high level of physical contaminants, a filtration system can also be used to help remove them from the system.

Selecting the Right Hydraulic Oil

With numerous hydraulic oils available on the market, selecting the one that best suits your system can be a challenging task. Several factors should be considered when choosing the most suitable hydraulic oil.

Factors to Consider When Choosing Hydraulic Oil

As with many oils, the first set of factors to consider when selecting an oil are the operational limits of the system and the oil. Typically, OEMs can guide users accordingly in this area, as they pay attention to the operating temperatures, pressures of the system, as well as the required viscosity of the oil.

Next, they need to consider the environment in which they are working. Are there any possibilities of the oil entering waterways or the soil? In such cases, environmentally friendly lubricants should be used.  They also need to determine if these oils will be exposed to harsher environmental conditions than regular ones. If this is the case, then they may consider utilizing synthetic oils instead of mineral oils.

Compatibility with Equipment and Seals

Most mineral hydraulic oils are compatible with seals and some metals. However, certain hydraulic oils are not. HFC fluids (Water polymer fire-resistant hydraulic fluids with water content >35%) react aggressively with tin and cadmium. As such, silicone rubber and Teflon are the materials utilized when these fluids are in use.

On the other hand, HFD fluids (water-free, synthetic fire-resistant hydraulic fluids) attack aluminum and aluminum alloys in the presence of friction stresses. Therefore, the only materials used with HFD oils are Viton and Teflon.

Due to the polar nature of environmentally friendly ester fluids, this causes significant swelling of conventional standard elastomers. On the other hand, Epikote and DD paints are resistant to HEPG (water-free, rapidly biodegradable polyalkylene glycols that are soluble in water), HFC, and HFD fluids to a certain extent. Therefore, the inside of tanks or other exposed surfaces should not be coated with these materials to avoid corrosion.

Environmental Regulations for Hydraulic Oil

Environmental lubricants are typically classified into three main categories:

Biodegradability – measure of the breakdown of a chemical (or chemical mixture) by microorganisms. This can be Primary (where there is a loss of one or more active groups that renders the compound inactive regarding that function) or Ultimate biodegradation (also known as mineralization, where the chemical compound is converted to carbon dioxide, water, and mineral salts).

Two additional operational properties that define biodegradability are inherently biodegradable (showing evidence of biodegradability in any test for biodegradability) and readily biodegradable (where a fraction of the compound is ultimately biodegradable within a specific time frame, as specified by a test method).  Figure 9 shows a table of internationally standardized test methods for measuring biodegradability.

Aquatic Toxicity – This refers to the effects of a chemical on organisms that live in water and is determined using organisms representing three trophic levels: algae or plants (primary producers), Invertebrates (primary consumers or secondary producers), and vertebrates (secondary consumers).

Acute toxicity is determined by exposing fish to a series of concentrations of a chemical over a short period. The concentration that is lethal to 50% of the test fish is calculated and expressed as the LC50 value.

On the other hand, Chronic Toxicity covers a longer exposure time. It examines the effects on hatching, growth, and survival to determine the NOEC (No Observed Effect Concentration) values, LOEC (Lowest Observed Effect Concentration), or ECx values, where x is a percentage and the concentration of a chemical at which that percentage of the population shows some effect. 

As seen in Figure 10, this is the list of OECD (Organization for Economic Co-operation and Development) Aquatic Toxicity Tests.

Bioaccumulation – this refers to the accumulation of chemicals within the tissues of an organism over time. Depending on the degradation rate of the chemical, this can lead to a buildup in the organism over time, ultimately resulting in adverse biological effects. The bioaccumulation potential of a compound is directly related to its water solubility. Figure 11 presents a summary of the bioaccumulation potential by base oil type.

 Overall, when investigating the environmentally acceptable properties of lubricants, we can compare their behavior based on their base oil type, as shown in Figure 12 below.

Additionally, a comparison of their features by type is illustrated in Figure 13.

Several labelling programs provide guidance for EALS. These are summarized below in Figure 14.

Tips for Storing and Disposing of Hydraulic Oil

Hydraulic oils are easily contaminated, particularly during storage and handling. Due to the tight clearances in hydraulic systems and their function of transmitting power, any contaminant can cause an issue with the system’s efficiency. As such, it is crucial to store and dispose of these oils properly.

Every ounce of contamination prevented during storage saves hours of troubleshooting later.

Proper storage of hydraulic oils includes keeping the containers closed and protected from the elements, as this prevents dirt particles from entering easily. These oils should not be stored in an area that is not covered or exposed to the elements, as this increases the risk of contamination. For any oil that is decanted into smaller containers, filters should be used during decanting (into a clean container) and upon decanting into the equipment to minimize the transfer of particles from the outside.

When hydraulic oil reaches the end of its life, it must be disposed of properly. In different countries, various rules and regulations govern this disposal. In many countries, a certificate of custody and chain of transfer is required when moving used hydraulic oils from the equipment site to the site where they are disposed of. Some waste oil removal companies ask that the hydraulic oils be separated from other oils, especially in cases where these will be re-refined to create new oils.

Global Market Size and Growth Projections

In 2021, the global size of the hydraulic fluid market was $7.6 billion, with a projected compound annual growth rate (CAGR) of 5.2% from 2022 to 2030. On the other hand, in 2021, the US hydraulic fluids market was valued at $654.5 million, as shown in Figure 15 below. They have an estimated compound annual growth rate (CAGR) of 4.8% from 2022 to 2030.

Key Drivers and Challenges in the Market

An increase in construction due to greater global demand for infrastructure is noted as one of the key factors driving the demand for hydraulic fluids. Previously, during the pandemic in 2020, there were supply chain issues that affected the delivery of base oils to many markets. Additionally, the Russia-Ukraine war has also led to supply shortages, disrupting the regular market demand.

Regional and Industry-specific Trends in Hydraulic Oil Consumption

While the global hydraulic fluid market size was $7.6B in 2021, the most prevalent sector was construction (25.3%) as seen in Figure 16 below. As initially noted, the construction sector has seen a significant increase, but this should not distract from the prevalence of hydraulics in many other industries, including metal and mining, oil and gas, Agriculture, Automotive, aerospace, and defense, to name a few. 

Emerging Technologies and Their Impact on the Market

As regulations regarding emissions and their impact on the environment become more stringent, we are seeing some movement towards EALs (Environmentally Acceptable Lubricants) and even synthetic hydraulic lubricants. Users are more aware of the environmental implications of hydraulic oils entering waterways and the overall CO2e associated with mineral oils compared to synthetic lubricants.

References

1. Mang, T., & Dresel, W. (2007). Lubricants and Lubrication 2nd Edition. Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA.
2. Hard Chrome Specialists. (2025, March 01). The History of Hydraulics. Retrieved from Hard Chrome Specialists: https://hcsplating.com/resources/hydraulic-systems-guide/history-of-hydraulics/
3. National Lubricating Grease Institute. (2025, March 01). Grease Glossary H1/H2/H3/3H/HX1. Retrieved from National Lubricating Grease Institute: https://www.nlgi.org/grease-glossary/h1-h2-h3-3h-hx1/
4. Totten, G. E. (2006). Handbook of Lubrication and Tribology Volume I Application and Maintenance Second Edition. Boca Raton: CRC Press, Taylor & Francis Group.
5. United States Environmental Protection Agency, Office of Wastewater Management, Washington, DC 20460. (2011, November). Environmentally Acceptable Lubricants, EPA 800‐R‐11‐002. Retrieved from U.S. Environmental Protection Agency: https://www3.epa.gov/npdes/pubs/vgp_environmentally_acceptable_lubricants.pdf
6. European Commssion. (2025, April 05). Aquatic toxicity. Retrieved from The Joint Research Centre: EU Science Hub: https://joint-research-centre.ec.europa.eu/projects-and-activities/reference-and-measurement/european-union-reference-laboratories/eu-reference-laboratory-alternatives-animal-testing-eurl-ecvam/alternative-methods-toxicity-testing/validated-test-methods-h
7. Houston, M. (2015). New EPA Regulations for Environmentally Acceptable Lubricants and their effect on the dredging industry. Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies’ “Dredging Summit and Expo 2015”, (pp. 384-391).
8. Grand View Research. (2022). Hydraulic Fluids Market Size, Share & Trends Analysis Report By Base Oil (Mineral Oil, Synthetic Oil, Bio-based Oil), By End-use (Construction, Oil & Gas, Agriculture, Metal & Mining), By Region, And Segment Forecasts, 2022 – 2030. San Francisco: Grand View Research.

Engine oil is a lubricating fluid designed to reduce friction and wear between moving parts inside an internal combustion engine, while also cooling, cleaning, and protecting components from corrosion and deposits.

While we may think that there are numerous car manufacturers globally, as of 2025, there are only slightly over 100 original equipment manufacturers (OEMs), but over 5,000 models. Whether it’s a luxury vehicle or a basic, functional one, they all require one thing to keep them running: lubricants (in the EV market, this can mean greases as opposed to traditional oils).

Parallel to the various models of vehicles, there are also numerous types of lubricants on the market, each designed specifically for different requirements. In this article, we will share some knowledge on the areas you need to be familiar with for these types of lubricants, and of course, what impacts they have on your vehicle of choice.

Understanding Viscosity and Engine Oil Grades

Before exploring the types of oils, it is essential to understand one of the most important characteristics of oil: its viscosity. This is what governs the engine’s functionality and, to some extent, dictates its performance.

What is Viscosity?

Oil viscosity is the internal friction within an oil that resists its flow. It measures the oil’s resistance to flow and is one of the most important factors in lubricants. Viscosity is also defined as the ratio of shear stress (pressure) to shear rate (flow rate).

The SAE Viscosity Rating System

The SAE (Society of Automotive Engineers) developed viscosity grades to classify engine oils, enabling engine manufacturers and oil marketers to make recommendations and label their products accordingly. The SAE J300 is a series of two viscosity grades: one with the W and one without the W.

Monogrades with the letter “W” are defined by maximum low-temperature cranking and pumping viscosities and a minimum kinematic viscosity at 100°C. (Typically, this represents the start-up condition of an engine.)

Monogrades without the W are based on a set of minimum and maximum kinematic viscosities at 100°C and a minimum high temperature / high shear measured at 150°C and 1 million reciprocal seconds (s^-1). (Typically, this represents the operating conditions of the engine when it is in use.)

Multiple viscosity grade oils or multigrades are defined by:

• Maximum low-temperature cranking and pumping viscosities
• A kinematic viscosity at 100°C that falls within the prescribed range of one of the non-W grade classifications
• A minimum high temperature / high shear viscosity at 150°C and 1 million reciprocal seconds (s^-1).

These represent the extremes of startup and engine operation.

The table below gives a summary of these.

API Certification

The American Petroleum Institute has a dedicated Engine Oil Licensing and Certification System (EOLCS), a voluntary license and certification program that authorizes engine oil marketers who meet the specified requirements to use their quality marks.

It is a cooperative effort amongst additive industries and vehicle and engine manufacturers such as Ford, General Motors, and Fiat Chrysler, which are represented by the Japan Automobile Manufacturers Association and the Truck and Engine Manufacturers Association. The performance requirements and test methods are established by vehicle and engine manufacturers, as well as technical societies and trade associations, including the ASTM, SAE, and the American Chemistry Council (ACC).

While the API initially included designations for both gasoline and diesel specifications, it later established these as two separate classes. Gasoline engines designed for cars, vans, and light trucks were allocated to the “S” or Service category. On the other hand, diesel engines designed for heavy-duty trucks and vehicles fall under the “C” or Commercial category.

These standards have been in place since 1947 and regulate both gasoline and diesel engine oils. One of the major changes since 2020 is the introduction of 0w16 oils, which now have their certification mark, the “shield” instead of the traditional “starburst”.

What’s the main difference between ILSAC GF-6A & 6B?

Both are designed to provide protection against low-speed pre-ignition (LSPI), timing chain wear protection, improved high-temperature deposit protection for pistons and turbochargers, more stringent control of sludge and varnish, enhanced fuel economy, and protection of the emission control system for engines operating on ethanol-containing fuels up to E85. However, ILSAC GF-6B applies only to 0W-16 oils.

The current gasoline engine oil standard is API SP. This standard was introduced in May 2020 and is designed to protect against low-speed pre-ignition (LSPI), provide timing chain wear protection, enhance high-temperature deposit protection for pistons and turbochargers, and implement more stringent control of sludge and varnish.

API SP with Resource Conserving matches ILSAC GF-6A by combining API SP performance with improved fuel economy and enhanced emission control system protection for engines operating on ethanol-containing fuels up to E85.

On the diesel side of things, there has been a slight break from tradition, as two new categories, CK-4 and FA-4, have been introduced. The main difference with these is the type of fuel used, specifically in terms of its sulphur concentration. CK-4 is ideally used for vehicles using diesel fuel with 500 ppm (0.05% weight) sulphur, while FA-4 is used for vehicles using diesel fuel with less than 15 ppm (0.0015% weight) sulphur, and they must be Xw30 oils.

CK-4 oils are used in high-speed four-stroke cycle diesel engines designed to meet 2017 model year on-highway and Tier 4 non-road exhaust emission standards, as well as previous models of diesel engines. They are formulated for use with diesel oils containing up to 500 ppm sulphur. However, if they are used alongside fuels containing more than 15 ppm sulphur, this can affect the exhaust after-treatment system durability or oil service drain interval.

They effectively sustain the durability of emission control systems, particularly when particulate filters and other advanced after-treatment systems are employed.

API CK-4 oils are designed to provide enhanced protection against oil oxidation, viscosity loss due to shear, and oil aeration, as well as protection against catalyst poisoning, particulate filter blocking, engine wear, piston deposits, degradation of low- and high-temperature properties, and soot-related viscosity increase.

FA-4 oils are specifically for certain Xw30 oils formulated for use in high-speed four-stroke cycle diesel engines designed to meet 2017 model year on-highway greenhouse gas emission standards. They are formulated for use in on-highway applications with diesel fuel sulphur content up to 15 ppm. These oils are blended to a high-temperature, high-shear (HTHS) viscosity range of 2.9cP – 3.2cP to assist in reducing greenhouse gas (GHG) emissions.

They are effective in sustaining the durability of emission control systems, particularly when particulate filters and other advanced after-treatment systems are employed.

API FA-4 oils are designed to provide enhanced protection against oil oxidation, viscosity loss due to shear, and oil aeration in addition to protection against catalyst poisoning, particulate filter blocking, engine wear, piston deposits, degradation of low and high-temperature properties, and soot-related viscosity increase. It is essential to note that FA-4 oils are not interchangeable or backward compatible with API CK-4, CJ-4, CI-4, CI-4 PLUS, and CH-4 oils.

An exhaustive list can be found here.

Choosing the Right Engine Oil Grade for Your Vehicle

This begins with understanding the requirements of your engine and the type of fuel it uses. As we saw above, various classifications exist, and when selecting diesel engines, we must pay particular attention to the concentration of sulphur in the fuel being used. This would be highly dependent on the availability of these fuels in the market, as not all countries have ready access to varying grades of fuel.

All original equipment manufacturers (OEMs) provide a recommended range of oils for your vehicle, typically listed in the vehicle’s owner’s manual. They typically provide various operating conditions and corresponding grades of oils to select. For example, for the Nissan Qashqai 2024 model with the HR13DDT engine, a 5w30 or 0w20 oil is recommended, but the manufacturer also provides this chart to guide the user:

It is important to consult with your Car manufacturer before purchasing the correct oil for your vehicle.

Common Misconceptions about Viscosity and Engine Oil Grades

Many people believe that “thicker” oil is better for their vehicle. This is the furthest thing from the truth! Over the years, engine sizes have been reduced dramatically. With this size reduction, we can infer that the clearances within the engines have also decreased. Hence, a “thicker” oil from 50 years ago will not suffice in a modern-day engine.

Think of trying to drink molasses with a thick (or wide) straw. This may be possible (although challenging), but if we swapped the thick straw for a thinner, narrower straw, the person would have to use significantly more force to pull up the molasses. A similar phenomenon occurs with engine oils.

In modern engines, the oil lines are narrower, so trying to force a heavier-weighted oil (such as straight 50) would put more pressure on the engine. This is where we begin to see leaks in the engine, particularly at the bottom of the sump near the seals, where the most pressure is exerted during start-up to pump the thicker oil to the top of the engine. However, if we used the correct viscosity of the oil, the engine would not be subjected to this amount of additional pressure. So “thicker” is not always better.

Another common misconception is that the number in front of the “w” in a multigrade oil represents the thickness of the oil, and if it’s zero, then it must be very thin! The number in front of the “w” for multigrade oils represents the viscosity of the oil at start-up conditions (typically 0°F or -17.8°C for Winter).

Hence, the lower the number, the faster the oil will flow at startup. As such, a 0w20 will get from the bottom of the sump to the top of the engine faster than a 20w50. In this case, the 0w20 will provide more protection during startup compared to the 20w50, as most wear occurs during this period.

On the other hand, the number behind the “w” indicates the viscosity at operating temperature. This is where a higher number may not always be agreeable, depending on the year of manufacture of your engine or the ambient conditions. When deciding which oil to use, both numbers (in front of the ‘w’ and behind the ‘w’) are important.

Types of Engine Oils

When you walk into the auto repair store, it can be quite overwhelming with the barrage of oils readily available for customers. It’s easy to get distracted by the shiny packaging or marketing claims (‘This is the best oil ever!’) when deciding to purchase oil for your vehicle. However, it begins with understanding the basics of engine oils.

Conventional Oil

This is the oil that has been around since the beginning of the automotive revolution. They are also referred to as mineral oils and represent the API Groups I-III base oils. Ideally, these oils can be traditionally found as the base for lubricants that are on the higher end of the viscosity spectrum (think 40, 50, and 60 weight).

These mineral oils are found on the earth, and their molecules may not all be the same size (unlike synthetic oils). They are usually less costly than synthetic oils but still provide some protection to the engines.

Synthetic Oil

Synthetics are considered the top-tier set of lubricants, as they can withstand harsher conditions compared to mineral oils. They are found in groups IV and V, and many of them are man-made, while others are naturally occurring. Most of their molecules are the same size, allowing for better properties, and they tend to be more expensive than mineral / conventional oils.

Synthetic Blend Oil

A synthetic blend oil refers to an oil that contains both synthetic and mineral base oils. However, there is no set ratio of synthetic to mineral oil that can impact the final performance of the lubricant to be classified as a synthetic blend. Many manufacturers can easily get away with using only 1% synthetic oil blended with 99% mineral oil and still label the oil as a “Synthetic blend.”

This gives the customer the false impression that they are purchasing an oil that will offer the best of both worlds.

High Mileage Oil

Until about a decade ago, high-mileage oils were not really that popular, but with the aging population of automobiles, there has been a significant increase in the purchase of this type of oil. Different manufacturers have varying specifications for these oils and typically use the vehicle’s mileage range to help guide customers in selecting the correct oil.

These oils are blended on the “thicker” side of the viscosity range, meaning on the higher end of the maximum viscosity. For instance, a regular 10w40 would appear to be “thinner” than a High Mileage 10w40. They are also reinforced with seal conditioners to help some of the seals in the older engines. But it does not contain magic, so it can’t repair your engine!

Racing Oil

The performance required of a Ferrari compared to that required of a minivan can differ drastically.  The operating conditions are starkly different, and the engines would require specifications from their manufacturers. As such, there are specially developed racing oils for these higher-performance vehicles built to withstand harsher conditions compared to the regular engines.

This does not mean that you should use racing oil in your regular vehicle to get the performance of a race car. The oils are blended for specific purposes and must be used accordingly to ensure maximum functionality. Similarly, the oil used in the minivan would not be able to withstand the conditions of a racing car. Use oil that is compatible with the type of engine and the required performance.

Benefits of Using the Right Engine Oil

As we’ve covered in this article, various types of engines require different levels of performance, and engine oils have been specifically designed for these conditions. Hence, it becomes critical to select the right engine oil for your engine. But what are some of the benefits of selecting the right oil?

Improved Fuel Efficiency

Firstly, the primary purpose of a lubricant is to reduce friction between contacting surfaces. By reducing the friction, a smaller amount of energy is required to perform the same amount of work. Overall, this leads to a more efficient system.

When we’re talking about engines, fuel is also required to produce energy for the engine to work. As engine oils have become more advanced, they have enabled significant improvements in fuel efficiency for many engines. This is one of the requirements in the API service categories. By selecting the incorrect viscosity of oil or type of oil for your vehicle, you can negatively impact the fuel efficiency, which in turn adds up to a higher fuel bill at the end of the month!

Longer Engine Life

The occurrence of wear is one of the most common challenges with engines. By using the correct oil (as recommended by the manufacturer), the viscosity of the oil is ideal for keeping the engine surfaces from touching, which can prevent wear.

Additionally, engine oils contain additives that can also help protect the oil and the engine’s components. Hence, with the right oil (as specified by your OEM), your engine will have the ideal conditions it needs to last longer compared to using an oil that does not provide the optimal protection.

Better Engine Performance

Engines were created with particular standards in mind. OEMs designed engines to withstand certain temperatures and conditions. These attributes are passed to lubricant suppliers who would design engine oils capable of withstanding and performing in these conditions. Using the recommended engine oil ensures better engine performance.

For instance, if the customer decides to use an API CK4 oil in their diesel engine but uses 500 ppm sulphur fuel, they can run the risk of poisoning their catalyst or damaging their aftertreatment devices. This would not lead to better engine performance! Therefore, it is essential to follow the OEM’s recommendations to achieve optimal engine performance.

Reduced Emissions

Many of the newer specified oils are designed to reduce emissions. However, the older spec oils were not developed with reducing emissions in mind. Hence, using an older-specification oil (API SL) in a vehicle manufactured in 2024 may not necessarily help reduce emissions. On the other hand, the API SP oil is designed with enhanced emission control in mind, making it ideal for reducing emissions.

Enhanced Lubrication and Protection

If we recall the straw example from earlier in this article, we will realize that engines have been designed for specific lubricants, both in terms of viscosity and additive packages. By using the recommended lubricants, we can ensure that our engines receive the necessary protection and have the correct amount of lubrication to prevent wear. Use lubricants specifically designed for your engine to ensure enhanced lubrication and protection.

Understanding the Different Engine Oil Change Intervals

At the beginning of this article, we reiterated that there are more than 5000 models of engines that exist. Every engine was built to different specifications, but they all provide the user with the ability to move the vehicle. With different manufacturers, there will also be varying oil specifications for each model, including the recommended oil change intervals. Let’s look at some of those.

Factors Affecting Oil Change Frequency

Lubricants are designed for certain conditions; however, if those conditions are exceeded, then the lubricant can degrade at a faster rate. For instance, if the driver frequently starts and stops or experiences prolonged periods of idling, these patterns can stress the oil more quickly, causing it to degrade.

If the fuel quality is not as expected, it may also contribute to the oil degrading more quickly. In such cases, users may opt for shorter oil change intervals to ensure their engine remains protected.

Another factor affecting the frequency of oil changes is the quality of the oil used. Typically, synthetic oils may have longer oil change intervals than mineral oils. However, there are some cases where the manufacturers advise the same interval length, whether mineral or synthetic.

Using Oil Analysis to Determine Engine Oil Life

There are instances where the oil drain interval can be extended beyond the manufacturer’s recommended interval. However, this must be done with guidance from a lab while utilizing oil analysis. Typically, some applications do not utilize the additives in the oil as quickly and may not require the regular oil change interval; instead, the oil remains healthy by the time it’s supposed to be discarded.

This can be considered a waste of resources. With oil analysis, one can monitor the health of the oil and determine if it is nearing the end of its useful life, allowing for informed decisions on whether to change it or not.

The Debate over Extended Oil Change Intervals

There will always be a debate over whether it is wise to extend the oil change intervals for equipment, as it goes against the manufacturer’s recommendations (or, in some cases, this could void the warranty). However, just as with blood testing (or condition monitoring for oil), close monitoring allows us to justify the outcomes of extending the intervals.

Some of the benefits of extending the intervals include reduced manpower, allowing staff to perform other critical duties, a reduction in oil consumption and its disposal, as well as reduced downtime for maintenance. One can also include the reduction of safety risk depending on the application. These all add up in the end, and the benefits of safely extending the intervals may outweigh remaining at the recommended intervals.

The Importance of Regular Engine Oil Changes

Some oil manufacturers claim that their oil, when added to your engine, will remain “golden” in color and not turn dark. Every engine produces soot /carbon as a byproduct, so if the oil does not change color, it means that the soot/carbon is likely remaining stuck on the insides of your engine, which can lead to engine failure.

In these cases, the oil, especially motor oil, contains detergent and dispersant additives that keep the soot or carbon suspended in the oil. This ensures that these deposits do not adhere to the engine’s internal components, causing clogging of smaller clearances and damaging the engine. Hence, an oil change removes these accumulated deposits. There are several other advantages to changing oil regularly for these engines.

Preventing Engine Wear and Tear

Motor oils are formulated with around 30% additives. These additives can perform various functions, including protecting the internal components from wear. However, over time, they become depleted and should be replenished. Changing your oil regularly can help with that. With an oil change, there is a replenishment of additives that protect the equipment.

Maintaining Proper Engine Functioning

Over time, the viscosity of the oil in engines will decrease due to the conditions that exist within the engine. There will come a time when it reaches the end of its life and will no longer be able to protect the engine. At this point, the crosshatch on the cylinder walls can begin to experience some polishing, as the oil can no longer provide the necessary protection. By changing the oil on time or regularly, this can be avoided, and the engine can maintain its proper functioning.

Avoiding Costly Repairs

When the oil starts to degrade, it loses all its protective elements, and wear can start to occur. With frequent oil changes, this can be avoided as new oil will be able to protect the engine and its components to the best of its ability. This way, increased wear can be minimized, and costly repairs can be avoided.

Following Manufacturer Recommendations

Manufacturers typically recommend oil changes every 5,000 to 7,000 kilometers for passenger cars; however, this interval can vary depending on driving habits, environmental conditions, and even the type of fuel used. Oils are designed to protect the engine, and when they reach the end of their life, they can no longer fully perform this function. By changing the oil regularly (or, in some cases, as recommended by the manufacturer), the engine’s lifespan can be extended.

Monitoring Oil Levels and Quality

In some passenger cars, engine manufacturers specify that there is a loss of oil over time. One manufacturer, Audi specifies that owners should top up 0.5 liters of oil every 1000km. As one can imagine, if there is no top-up or oil replenishment, the oil levels can fall below the minimum value, causing damage to the engine.

Hence, it is essential to follow your manufacturer’s recommendations for topping up your engine to prevent damage. These top-ups also serve to replenish some of the used additives, providing additional protection for your engine.

Effects of Using the Wrong Engine Oil

Sometimes, the wrong engine oil is used. Whether it’s an issue of the unavailability of the correct stock or trying to standardize across the fleet without consulting the manufacturer’s recommendations, numerous issues can arise when the wrong engine oil is used.

Engine Sludge Build-Up

One of the most common side effects of using the wrong oil is a build-up of engine sludge. If we recheck the API standards, oils were designed to reduce sludge formation. When the incorrect oil is used, it cannot adequately compensate for the engine’s conditions, simply because it wasn’t designed for that purpose.

This can also occur when oil is used with an incorrect viscosity or with the wrong fuel (specifically, the concentration of sulphur for diesel engines).

Increased Friction and Wear

Earlier, we discussed how OEMs typically recommend several different types of viscosity for engines, depending on the specific conditions. However, if a viscosity is used that is too low to provide the correct amount of support and separation between the two surfaces, then increased friction and wear can result, damaging the engine’s internals.

Poor Performance and Efficiency

With the incorrect engine oil, the engine will not perform at its expected efficiency. This will directly impact its overall performance. If the viscosity exceeds the recommended value, the engine must work harder to achieve the same results, resulting in poor performance and decreased efficiency. Similarly, if the viscosity is lower than the recommended value, increased friction will result, leading to higher heat and reduced engine efficiency.

Damage to Engine Components

As stated above, a viscosity that is either higher or lower than the recommended value can damage the equipment’s internal components. Similarly, if an incorrectly specified product is used, it may not withstand the engine’s regular environmental conditions and can break down prematurely, damaging its components.

Potential for Engine Failure

Using the incorrect oil, the engine’s components will not receive the necessary protection, whether it’s due to the incorrect viscosity or the wrong mix of additives. This can lead to premature oil degradation, which in turn may result in engine failure. The correct oil will be able to protect against these harmful conditions and keep the engine from failing due to lubricant-related issues.

How to Properly Dispose of Used Engine Oil

Changing our motor oil is important and must be done regularly, but how do we dispose of the used oil in a safe and environmentally friendly manner? Approximately 42 gallons of crude oil are required to produce 0.5 gallons of new oil for lubricants. However, only one gallon of used oil needs to be converted into 0.5 gallons of new oil.

Hence, recycling used oil significantly reduces the number of resources required to produce new oil. There are numerous benefits to recycling used oil, which can help in the fight against declining resources. Let’s dive into this a bit more.

Environmental Impact of Improper Disposal

When motor oil reaches the end of its life, it can become contaminated with harmful pollutants, which can negatively impact the environment if improperly disposed of. Some of these can be toxic to plants, and it only takes the used oil from one oil change to contaminate one million gallons of fresh water!  Therefore, we need to be mindful of the disposal of our oils.

Used motor oil can typically contain metal fillings (from engine wear), chemicals from by-products, and possibly fuel. Improper disposal, especially into waterways, can disrupt the supply of clean drinking water for many people. If this used oil seeps into the soil, it could also contaminate the water table and negatively impact plants and, by extension, humans who may consume these plants at some point.

Laws and Regulations for Disposing of Oil

The EPA (United States Environmental Protection Agency) provides guidelines in Title 40 of the Code of Federal Regulations, specifically CFR part 279, regarding the disposal of used oil. In the UAE, there are strict guidelines for the disposal of used oil; otherwise, individuals may face severe fines and legal action. These used oils should never be poured down drains, onto the ground, or into bodies of water.

Community Recycling Programs

Some communities have a local collection point for used motor oils, which they then take to the larger refineries. This way, a larger volume of oil is collected and recycled by the refineries.

Tips for Safe and Responsible Oil Disposal

Motor oils contain 30% additives; therefore, mixing them with other used oils may not be the best option for those trying to recycle them. Ideally, these oils can be reconditioned (where they are cleaned up) or re-refined (where they are reused as base stock). Collecting your used motor oil in a clean container and taking it to your local recycling facility, where it will be properly disposed of.

Some facilities may burn it to process it for energy recovery, using it as fuel after removing the water and contaminants. One gallon of used oil processed for fuel contains about 140,000 British thermal Units (Btus) of energy. Regardless of the method you choose to dispose of your used motor oil, ensure you do not harm the environment.

The Evolution of Engine Oil

History of Engine Oil

Over time, engine oils have undergone significant evolution. Initially, there were only monograde oils, which had to be replaced seasonally. During the summertime, one oil could withstand the higher temperatures, and during the winter months, another oil was designed for those cold starts. This eventually led to the multigrade revolution, which allowed for the best of both worlds.

As we transitioned from monograde to multigrade, developments in the base oil sector continued, and we saw the rise of Group II mineral base oils. This eventually led to increased the production of Group III base oils and the development of their “hybrid” or Group III+ counterparts, which exhibit quasi-synthetic traits. As we evolved, introducing synthetic base oils as first fills for cars also became a new trend.

We have also seen the transition of straight mineral oils (50 or 60 weight) go down to 0W-16, unfathomable 20 years ago. The introduction of high-mileage oils was also a significant change in the industry, as cars became older, but owners needed to preserve their engines.

Over time, OEMs developed more specific standards as they designed their engines with greater precision, smaller spaces, and higher horsepower. One such standard is the BMW LL04 oils, which are fully synthetic and branded as long-life oils. This standard did not exist 50 years ago!

Improvements in Oil Technologies

Oil technologies have undergone significant improvements over the years. From refined base stocks to more balanced additives that consider the full impact of the oil, technology continues to improve. Technologies were forced to improve as OEMs made engine sizes smaller and more compact, but placed the oil under more stress. As such, oil manufacturers had to develop new methods to address more complex oil handling issues.

Shift Towards Synthetic Oils

Synthetic oils offered a solution that provided longer oil life and withstood harsher conditions compared to mineral oils. These oils provided the protection needed by more modern engines. Today, many auto manufacturers explicitly state that they prefer the use of fully synthetic oils in their engines for the entire lifetime of the vehicle.

Future of Engine Oil

Gasoline and diesel engines are likely to remain in use for quite some time. They won’t be coming off the market soon, as it would require 80% of the car population to have an early retirement. The spin-off to this is that car owners would also have to make significantly large investments in new vehicles.

We are witnessing the rise of alternative fuel engines, such as methanol and hydrogen, which are gradually making their way into mainstream areas. Even if it’s a new fuel source for engines, one thing that will not change is the need for moving parts. In any engine, there will always be moving parts that require some form of lubricant to reduce the friction, heat, and wear that can be generated.

Therefore, there will always be the need for lubricants, it’s just that the application and type may change or evolve over time.

Impact of Electric Vehicles on the Engine Oil Industry

One of the major developments in the automotive industry was the introduction of electric vehicles. However, one may argue that this concept has been around for more than 50 years; however, it has only recently entered the market due to an increase in manufacturing capability.

Many oil suppliers initially thought that this was the end of passenger car motor oils since the main “engine” was now an electric motor. However, this just changed the mode of lubrication to more grease applications for this part of the vehicle.

While electric vehicles are expected to continue growing in various markets, we can anticipate a decline in the volume of engine oil consumed. However, this does not mean that the innovation with engine oils will stop. More likely than not, it will continue as engine manufacturers are pushed to greater limits regarding carbon emissions and other stringent regulations.

References

American Petroleum Institute. (2023). API 1509 – Engine Oil Licensing and Certification System – Annex F. Washington: API Publishing Services.

American Petroleum Institute. (2025, January 18). API’s Motor Oil Guide. Retrieved from American Petroleum Institute: https://www.api.org/-/media/Files/Certification/Engine-Oil-Diesel/Publications/Motor%20Oil%20Guide%201020.pdf

American Petroleum Institute. (2025, January 18). Engine Oil Licensing & Certification System (EOLCS). Retrieved from American Petroleum Institute: https://www.api.org/products-and-services/engine-oil

Gulf Oil Lubricants. (2025, January 19). Your guide for using and disposing of Car oil. Retrieved from Gulf Oil Blog: https://me.gulfoilltd.com/en/blog/your-guide-for-using-and-disposing-of-engine-oil

Mathura, S. (2023, March 26). Oil Viscosity: A Practical Guide. Retrieved from Precision Lubrication Magazine: https://precisionlubrication.com/articles/oil-viscosity/

Motorway. (2025, January 18). How many different car brands are there? Retrieved from motorway: https://motorway.co.uk/sell-my-car/guides/how-many-different-car-brands-are-there

Sinclair Group. (2025, January 19). Do I need to top up my Audi’s engine oil. Retrieved from Sinclair Group: https://www.sinclairgroup.co.uk/news/audi-engine-oil/

United States Environmental Protection Agency. (2025, January 19). Managing Used Oil: Answers to Frequent Questions for Businesses. Retrieved from United States Environmental Protection Agency: https://www.epa.gov/hw/managing-used-oil-answers-frequent-questions-businesses

United States Environmental Protection Agency. (2025, January 19). Managing, Reusing, and Recycling Used Oil. Retrieved from United States Environmental Protection Agency: https://www.epa.gov/recycle/managing-reusing-and-recycling-used-oil

What is Lubrication?

Lubrication is the process of reducing friction, wear, and heat between moving surfaces by introducing a lubricating substance, such as oil or grease.

The Purpose of Lubrication

If you walk into any industrial facility, you will find lubricants. While they come in all types of textures (greases or oils), viscosities, and packaging, one thing remains true: We need them. Lubricants were designed to reduce friction as their main function. However, that’s not their only use.

Although lubricants can effectively reduce friction, they can also reduce or transfer the heat built up in machines.

Although lubricants can effectively reduce friction, they can also reduce or transfer the heat built up in machines. This only applies to oils circulated through the systems and not grease that remains in place.

Additionally, lubricants can minimize wear by providing an adequate film to separate surfaces from rubbing on each other.

Lubricants also help improve the efficiency of the machine by removing heat and reducing friction. They can also remove contaminants (for oils that are circulating, not grease) and transport them away from the machine’s internals. This is due to some additive technologies (such as dispersants or detergents).

Depending on the type of lubricant or its application, its function can also change. For instance, hydraulic oils are specifically used to transmit power, something that gear oils or motor oils cannot do. On the other hand, the lubricant can be considered a conduit of information if condition monitoring is considered.

Lubricants provide several functions depending on their application and environment. However, the main functions of a lubricant include reducing friction and wear, distributing heat, removing contaminants, and improving efficiency.

How Lubrication Reduces Friction and Wear

At the heart of lubrication is the main function of overcoming friction. When two parts move or two surfaces rub against each other, microscopic projections called asperities exist. Even on what appears to be smooth surfaces, asperities exist, and when these move over each other, friction is produced, which in turn can generate heat and cause wear.

Wear can typically occur in various forms, but in many of these, the touching of the asperities serves as the trigger point for wear to occur.

This is where lubricants really make a statement. They serve to provide a barrier between the two surfaces, almost allowing them to float over each other seamlessly. As such, friction is reduced once the asperities are kept apart, and this even influences a reduction in the occurrence of wear.

Wear can typically occur in various forms, but in many of these, the touching of the asperities serves as the trigger point for wear to occur. With the presence of the appropriate viscosity of lubricants, these asperities can be kept apart, and the occurrence of wear can be diminished significantly.

The Role of Lubrication in Preventive Maintenance

As we have noted above, proper lubrication can help to prevent wear. This is one of the many characteristics which make it ideally suited as a tool for preventive maintenance.

As defined, preventive maintenance can help maintenance professionals schedule time-based tasks / prescribed intervals¹. Any maintenance manual will include prescribed intervals at which lubricants should be changed (typically after 500 hours or 5000km).

OEMs (Original Equipment Manufacturers) defined these intervals as general guidelines for machine operators. This gives operators an idea of the lubricant’s expected life or the duration after which it would no longer be able to perform its functions adequately. By changing the lubricants at these intervals, one could avoid unplanned downtime.

Another aspect of lubrication associated with preventive maintenance is relubrication intervals. In some machines, there are minimum required reservoir levels that need to be maintained.

However, depending on the system, there may be some expected loss of lubricants during its lifetime. As such, relubrication intervals can help prevent unwanted downtime by injecting new oil or grease (with fresh additives) and maintaining the required reservoir levels.

Types of Lubricants and Their Applications

Not all lubricants are created equally! In fact, they need to be designed differently for the various applications in which they are to be used. Typically, the overarching classification of lubricants can fall under either oil or grease. However, there are further categorizations that also include solid lubricants and specialty lubricants, as there are many varying applications of lubricants.

Oil Lubricants: Characteristics and Uses

Most of us are very familiar with oils. They are liquid; we use them in our cars or trucks, but what are they? An oil is comprised of base oil and additives. The additives can be used to either enhance, suppress, or add new characteristics to the base oils².

Typically, oils can be used in many different applications and provide the advantages of having various viscosities according to the application³. These can range from oils with a viscosity similar to that of water to oils as thick as tar.

One of the main advantages of using oils as lubricants is their ability to dissipate heat from the system. Since they are fluid and circulate, they can “move” heat away from specific components and even help to remove some contaminants.

Oils can be used in gasoline-engine passenger cars, diesel-engine applications, circulating systems, turbines, gear applications, hydraulics, compressors, or even natural gas engines. Each application represents a different ratio of additives to base oils, ranging from 30% (motor oils) to a mere 1% additive (turbine oils).

Grease Lubricants: Advantages and Limitations

While the industry is familiar with oils as lubricants, there are some places where grease works better than oils! Greases are oils to which a thickener has been added. As such, they comprise base oil, additives, and thickener. The thickener holds the oil in place, allowing it to perform its main functions of reducing friction and providing lubrication.

One of the main advantages of greases is their ability to stay in one place. Consider a bearing placed at a 90° or 180° angle. If oil were used to lubricate this, it would drain out very easily. However, grease stays in place and still ensures that lubrication occurs.

While staying in place is a major advantage of grease, there are also some disadvantages to using it. A couple of those include the fact that grease cannot transfer heat away from components and keeps contaminants in place. These can both negatively impact the equipment.

Similar to oil, grease has different viscosities as per the NLGI (National Lubricating Grease Institute). These range from a 000 (almost the consistency of oil) to a 6 (similar to that of a block) and are all made for varying applications, as shown in the figure below.

While these viscosities define the application, one must also remember that the base oil viscosity can also differ. As such, operators must be mindful of NLGI grade, base oil viscosity, and additive package when selecting an appropriate grease.

Solid Lubricants: When and Why to Use Them

Why do we need a solid lubricant if we already have oils and greases in different states? Particular applications make these lubricants mandatory as they are the only ones that can meet the conditions and specifications involved.

Unlike oils or greases, these solid lubricants are designed to work in one lubrication regime, boundary lubrication⁴ (more on this later in the article). What sets these lubricants apart is their ability to form very thin films on the surfaces of moving components, which reduces friction due to their very low shear strength.

Some examples of solid lubricants include graphite, Molybdenum Disulfide (MoS2), Boren Nitride, and Fluoropolymer (PTFE). These solid lubricants can usually be used as grease additives (such as MoS2 for greases in mining with high load, low-speed applications) or even in the space industry for dry lubricant coatings on spacecraft.

Lubrication Regimes: Understanding the Science of Lubrication

The primary purpose of lubrication is to create an acceptable lubricant film to sufficiently keep the two moving surfaces apart while allowing them to move with reduced friction. This is the ideal condition, but a lubricant can undergo a couple of different regimes before it achieves this full film format.

The figure below shows the overall relationship between film thickness and the related regime and the associated regime relationships with the coefficient of friction.

Boundary Lubrication

At startup or rest, lubricants are usually residing in the sump. For this example, let us think about a car at rest. Since the vehicle has not moved, all the oil should have been drained and settled in its sump at the bottom of the engine. When the car starts, all the parts on the inside will begin moving.

Only after it starts does the oil begin its swift journey from the bottom of the sump to all the moving parts. That means that there is a delay between the oil getting to perform its function or reaching the moving parts.

In boundary lubrication, the oil has not fully formed its film, and there isn’t adequate separation of the asperities.

During boundary lubrication, the oil has not fully formed its film, and there isn’t adequate separation of the asperities. In this state, wear can still occur, and it is in this state that most wear occurs. A similar situation occurs during equipment shutdown, where the components also experience this boundary state of lubrication.

The figure below shows the various film conditions. In boundary lubrication (c), the asperities touch, whereas they are fully separated in (a).

Surface-active additives are critical for boundary lubrication and become activated under certain conditions. One of the most popular additives is EP (Extreme pressure) additives, which become activated when temperatures are increased (usually as a result of increased friction).

A surface film is typically formed during boundary lubrication. This can be the result of physical adsorption (physisorption), Chemical adsorption, or Chemical reactions involving or not involving stearate.

Physical adsorption occurs under mild sliding conditions with light loads and low temperatures. Chemical adsorption (chemisorption), stronger than physisorption, occurs when fatty acids react with metals to form soaps, which may or may not be attached to the surface.

On the other hand, chemical reactions that do not involve a substrate allow for slightly stronger bonds than chemisorption. However, with phosphorus-containing compounds, the phosphorus exists in a soluble carrier molecule that degrades at elevated temperatures, plates out on the metal surfaces, and forms a phosphorus soap (typically found in the Antiwear additive packages).

The last and strongest bonds to protect the surface are the chemical reactions involving a substrate where sulfide layers are formed on the surface. These provide low friction and good adhesive wear resistance⁵.

Mixed Lubrication

This state of lubrication exists as the lubricant transitions between Boundary and Full-Film lubrication. Its average film thickness is less than 1 but greater than 0.01μm. Some exposed asperities and roller element bearings can still experience this state during their start-stop cycles or if they are experiencing excessive or shock loads. These thin films are exposed to high shear conditions, leading to increased temperatures and reducing the lubricants’ viscosity⁶.

During this state, antiwear and EP additives protect the surfaces (similar to boundary lubrication). Most lubricants transition through this phase, and the additive packages must be able to help protect the surfaces.

Hydrodynamic Lubrication

During this regime, the two surfaces are usually fully separated. They are thick hydrodynamic fluid films that tend to be more than 0.001 inches (25μm) in depth, experiencing pressures between 50-300psi⁷. Ideally, friction only results from the shearing forces of a viscous lubricant⁸.

In this state, the surfaces are conformal, meaning that the angles between the intersecting surfaces remain unchanged. It is important to remember this, as it differentiates the hydrodynamic regime from the elastohydrodynamic regime. As shown in the figure below, the coefficient of friction changes for the various regimes, with the hydrodynamic regime having the lowest value.

Elastohydrodynamic Lubrication (EHL)

One of the main defining factors with EHL is that the oil’s viscosity must increase as the pressure on the oil increases, such that a supporting film must be established at the very high-pressure contact areas. Due to the pressure of the lubricant, elastic deformation of the two surfaces in contact will occur. These films are thin, typically around 10-50 μinches (0.25 – 1.25μm).

The surfaces in EHL are non-conformal (unlike Hydrodynamic lubrication), and the asperities of the contacting surfaces do not touch. However, the high pressures can deform either of the contacting surfaces to ensure that a full fluid film is maintained. This can increase the coefficient of friction.

Common Lubrication Mistakes and How to Avoid Them

Mistakes can happen all the time, but when we repeat them, they can become a habit or, worse, be viewed as a “best practice” within our industry. In the lubrication realm, there are a few common mistakes that occur quite frequently. In some cases, the operators may not understand or be aware of the full gravity of these mistakes. In this section, we will explore ways to avoid these mistakes.

Over-Lubrication vs. Under-Lubrication

“Some grease is better than no grease” is a common saying in the industry. However, there is such a thing as over-lubrication! Think about swimming pools. The pool usually has different levels: a minimum fill level, then a mid-tier level, and finally, the maximum level.

If we don’t fill it to the minimum level, it’s basically a puddle of water, not a swimming pool. We need a certain volume of water to function as a swimming pool. The same applies to our equipment.

We will under-lubricate our equipment if we do not provide enough grease or oil. In these cases, there is not enough lubricant to form the full required film to keep the two moving surfaces apart and perform all the lubricant functions. Therefore, there will be increased friction, wear, and heat, all leading to system inefficiencies.

On the other hand, if we filled the swimming pool beyond the maximum level, it would be pretty tricky for us to stand in it (while touching the bottom) or walk across the length of the pool without having lots of opposition from the water compared to walking across the length of the pool when it’s filled mid-way.

Something similar is happening with our equipment. If we over-lubricate it, we place additional stress on the components to perform extra work, as they must move on a thicker layer of lubricant, which will cause frictional losses. This can cause the equipment to heat up, leading to degradation of the lubricant and loss of efficiency.

Both over-lubrication and under-lubrication can be detrimental to your equipment. Instead, use the optimal level of lubricant, or (in the case of greases) use ultrasound to determine the required amount of grease for your application. In both cases, the ideal amount of lubricant is the volume at which the coefficient of friction is significantly lowered.

Choosing the Wrong Lubricant for the Application

Quite often, the wrong lubricant is chosen for the application. This can happen in several ways, whether unintentional or an error passed down through shift changes. Selecting the correct lubricant for your application begins with knowing the environmental and operational conditions and the equipment specifications.

Your first guide/resource should be the equipment’s OEM. They designed the equipment to perform within specific tolerance limits and can advise on the most appropriate lubricant given these tolerances. If they cannot be contacted, an alternative would be contacting your lubricant supplier to help determine the best lubricant based on their expertise with similar types of equipment in varying conditions.

Selecting the correct lubricant for your application begins with knowing the environmental and operational conditions and the equipment specifications.

Another misconception about selecting lubricants is that they should be chosen based on their initial cost. Instead, the total lifecycle cost of the lubricant should be considered, and the properties of the lubricant should also be factored into the decision-making process. The initial cost of the lubricant pales compared to the cost associated with unplanned downtimes, the short life span of the lubricant, and its disposal.

Inadequate Lubricant Storage and Handling

Lubricants should be handled with care. They can be affected by temperature, light, water, particulate, or even atmospheric contamination. They must be stored properly in a dry, clean, cool space (not exposed to the elements).

When transferring lubricants from larger containers into smaller ones, think of how you would perform this operation if you transferred blood from the blood bank to one of your family members. Would you use any container you found on the ground, or would you ensure that it is a sterilized container (needle or equipment)?

Lubricants can easily become contaminated with particulates, which can then be transferred to machines, leading to unplanned shutdowns. When transferring lubricants, it is critical to ensure that we do not introduce contaminants or transfer these contaminants to our equipment. We must keep the lubricants clean and free from contaminants.

Ignoring Environmental and Operational Conditions

Not all lubricants are created equally. Some are designed for harsher environments, while others can only function in regular operating conditions. Mineral oils can typically work in many circumstances. However, when higher temperatures or loads are involved, this may be a job more suited for a synthetic lubricant.

On the other hand, if the lubricants are geographically close to waterways or come into contact with them in any way, then these should be environmentally acceptable lubricants (EALs). Depending on the load and temperatures experienced by your equipment, your lubricant provider or OEM for the machinery can advise on the best-suited lubricant that will perform in these conditions.

Lubrication Maintenance Best Practices

We’ve already covered some mistakes; it’s time to look forward to some lubrication best practices. To some of us, these may seem trivial, but they can lead to big impacts on your overall maintenance budget and can even manage to decrease some unplanned downtime.

Creating a Lubrication Maintenance Schedule

Every component in your industrial facility needs to be lubricated. The frequency at which this occurs, alongside the type of lubricant, can vary greatly. However, by properly mapping out your lubrication points and frequency intervals, you can develop a lubrication maintenance schedule that your planner will be proud of!

The first task on your list would be to have a detailed listing of all your assets, their locations, the type of lubricant being used, and suggested relubrication frequency. Next, this can be consolidated into daily, weekly, monthly, and quarterly tasks.

Afterward, you must bring your mapping skills into place as you incorporate the lubrication tasks with other maintenance tasks in the same area. This way, your assigned personnel maximize their time in one geographical location.

Importance of Lubricant Analysis and Condition Monitoring

How often do you perform blood work for yourself or visit your doctor? Performing blood work is similar to taking an oil sample for our equipment as we investigate what’s happening inside it. This can give us a heads-up on an impending failure (if there is a high wear metal concentration or the presence of contaminants) or an issue in the oil (changes in viscosity or additive packages).

By effectively monitoring the health of your oil, you can prevent unplanned shutdowns or even extend its life. This can save your company from significant losses and increase your production output.

Lubrication Training for Maintenance Teams

Quite often in our industry, we hear, “Oil is oil, or grease is grease,” but after reading this article, I’m sure you will agree that those words are a very big misrepresentation. This is why training is so important for our teams. We want to ensure we all understand why we’re not leaving the oil drums out in the rain and pouring them into our equipment!

This will lead to water getting into the oil drums. Then, we include the water in our equipment alongside our oil, which will change the oil’s viscosity, possibly leech out some of the additives being used for protection, and can act as a catalyst for further, rapid degradation of the oil.

This simple storage and handling concept can cost our company unplanned downtime and loss to production, but by adequately training our teams to understand lubrication and some of the best practices, we can transform our facilities into world-class lubrication sites. The only way to do this is as a team working together to achieve a goal that we all understand.

Frequently Asked Questions About Lubrication

How Often Should Equipment Be Lubricated?

This can change depending on your environment and operating conditions. A machine operating in a clean environment with ambient temperatures and a typical load should be lubricated according to its schedule. However, if this same machine is in a dusty, high-temperature environment working 24/7, its change or relubrication intervals will be shorter than the regular ones.

Lubrication reduces friction in your system. Hence, you can detect when friction levels increase if you’re monitoring your assets using ultrasound. This would allow you to apply a small volume of lubricant to lower these levels. (This is specifically for greases.)

You are always advised to check with your OEM, who will have recommended lubrication schedules for your equipment in varying environments and operating conditions.

What Are the Signs of Poor Lubrication?

Poor lubrication can mean under- or over-lubricated assets or incorrect use of a lubricant in a particular application. If your lubricant is not meeting the expected intervals and the components constantly fail due to lubrication issues, these are some telltale signs of poor lubrication.

How Do I Know If I’m Using the Right Lubricant?

All lubricants are required to meet standards to prove their performance, or OEMs may approve some for their suited applications. The lubricant’s performance standards should be compared to those outlined by the OEM for a particular piece of equipment. If they don’t match or there are discrepancies, then the OEM or lubricant supplier should be contacted for verification. Sometimes, an over-qualified lubricant may be used in your application, and it can also give you the expected results, but of course, at a higher cost.

Lubricants are the lifeblood of our equipment and keep our industry moving. We need to understand them fully, their roles in our equipment, and how we can optimize them for maximum performance.

References

1. Debshaw, B. (2023, February 02). Reducing Costs, Increasing Production: The Remarkable Impact of Predictive Maintenance. Retrieved from Precision Lubrication Magazine: https://precisionlubrication.com/articles/predictive-maintenance/
2. Mathura, S. (2024, April 01). Lubricant Additives: A Comprehensive Guide. Retrieved from Precision Lubrication Magazine: https://precisionlubrication.com/articles/lubricant-additives/
3. Mathura, S. (2023, March 26). Oil viscosity: A practical guide. Retrieved from Precision Lubrication Magazine: https://precisionlubrication.com/articles/oil-viscosity/
4. Britton, R. (2023, January 26). How do Solid Lubricants work? Retrieved from Precision Lubrication Magazine: https://precisionlubrication.com/articles/solid-lubricants/
5. Hamrock, B. J., Schmid, S. R., & Jacobson, B. O. (2004). Fundamentals of Fluid Film Lubrication Second Edition. New York: Marcel Dekker Inc.
6. Pirro, D. M., Webster, M., & Daschner, E. (2016). Lubrication Fundamentals, Third Edition, Revised and Expanded. Boca Raton: CRC Press.
7. Pirro, D. M., Webster, M., & Daschner, E. (2016). Lubrication Fundamentals, Third Edition, Revised and Expanded. Boca Raton: CRC Press.
8. Hamrock, B. J., Schmid, S. R., & Jacobson, B. O. (2004). Fundamentals of Fluid Film Lubrication Second Edition. New York: Marcel Dekker Inc.

When we walk into a pharmacy, there are thousands of items. Some of them do the same job but have different names and price points, while others are specialty items designed to solve a particular problem at a slightly elevated price point. Some of these may not be readily available in all pharmacies. Machinery lubricants adopt a similar type of pattern.

There are various OEMs on the market that all produce finished lubricants. Some of the majors are Shell lubricants, ExxonMobil, Total, and Castrol, while there are other niche producers who handle very specific markets. Like the pharmacy, where numerous choices solve the same issue, we have machinery lubricants from different suppliers who meet most of the standard specifications or specialty-grade products.

Each supplier will have a proprietary blend that comes from an invested amount of Research and Development into their product to produce something that meets international equipment specifications and regulatory standards.

Does this mean that one product is better than the other, or does it mean that all hydraulic oils (for instance) are the same? This depends on the application.

The hydraulic oil used to top up the compactor of a garbage truck with several leaks will not be the same hydraulic oil that we use for a critical hydraulic system in a power plant, which requires fire-resistant oil. We can also compare the engine oil used for a 40-year-old regular car to that of the engine oil used in a McLaren race car on race day.

Different applications have varying risks associated with them, as well as performance expectations; this is what sets certain lubricants apart.  

The 5S Methodology

While some may be familiar with the 5S methodology of lean principles, this may be the first time others have heard of its existence. In essence, these principles help to maintain quality standards within the workplace. As per (ASQ, 2024), 5S is a quality tool derived from 5 Japanese terms used to create a workplace suited for visual control and lean production. The 5 pillars and their translations are listed in Table 1 below.

We can use these principles to adopt a leaner approach to lubricant consolidation in our facilities. This way, we ensure that our operators have a clean, manageable workplace when handling lubricants. The 5S method can give us a better overall view of what happens in our lubricant storage areas.

Let’s “Sort’ This Out

When walking into many facilities, there are usually a lot of oil drums, buckets, or items used for lubrication scattered all over the facility. However, some facilities are fully equipped, nicely stocked, and have dedicated lube rooms. The first step in our process is determining what is needed and what is not.

In this case, the best place to start is with an inventory list developed by physically identifying the items on the plant. If this is the first time this exercise is being conducted, then it is critical to perform this check in person rather than rely on the information entered into the CMMS (if one exists). Sometimes, not all the information may have been captured in the CMMS when it was entered initially.

A good idea would be to divide the plant into various sections and perform your audit one section at a time. It would be ideal to note the following during your audit:

• Name of the lubricant (for example, Turbo S4GX)
• OEM (for example, Shell)
• Viscosity grade (ISO 46)
• Expiry date (use this opportunity to find out if you have expired lubricants in stock)
• Quantity (use this opportunity to find out if the inventory levels are accurately reflected in your CMMS).

Armed with this information, we can correlate this to the equipment needing the associated lubricant. In this instance, we can compile an asset listing and assign which lubricants are used for the respective assets. With the asset listing, we should also identify the oil requirements for the specified component. This way, we can develop a table similar to Table 2 below.

With the information collected in Table 2, we can easily sort through the lubricants we have in use and match them back to the requirements of the assets. This is where we can identify if we have duplicated products or products that serve the same function but are represented by different brands. This is the beginning of the consolidation process.

If you enter this information electronically, it will be easy to sort. You can group similar applications together and then compare the application’s requirements to the current lubricant. This will help you determine if you are using a highly specialized lubricant for an ordinary application or if the incorrect lubricant was used from inception!

This exercise will be fundamental in gauging your lubrication requirements and then allow you to consolidate some of the lubricants in use. For instance, if there are five different applications of gear oil and many types of oil, we would need to determine if all the listed lubricants are entirely necessary. See Table 3 below and determine if we need these five types of gear oil.

We can begin with the types of oils listed; some have varying viscosities, while others are food grade, and the rest are not. We can include this in a summary table, as seen in Table 4:

Table 4 shows that GB 1005, GB-4005 & GB-4008 all require the same type of oil, a food-grade ISO 220 mineral gear oil. Then why do we have three different types of oils that match the exact description? We can consolidate this oil into just one food-grade ISO 220 mineral gear oil brand. Ideally, the choice will be based on the supplier relationship, the availability of the product, and other cost factors, including delivery to the site.

We can also see that GB-2009 and GB-3003 require a non-food grade ISO 460 oil; however, one is synthetic, and the other is mineral. In this case, we can review our asset specifications and determine if a synthetic was required or if a mineral oil is preferred for these applications.

In this case, we could be using a higher-specification product and paying a lot more when the asset does not require it. This decision could have occurred in the past when synthetic oil was the only available grade of oil for that component, and it was ordered from the supplier to keep the plant running. However, if we consolidate these two, then we could go with a regular mineral non-food grade ISO 460 oil for both applications. 

By understanding our applications and where we’re using these oils, we’ve just cut down our list of 5 gear lubricants to 2 gear lubricants! These will be much easier to manage in our inventory than keeping track and ordering from 5 different suppliers.

Additionally, your staff will have less to worry about as they know which specific oil is for the ISO 220 grades and which one is for the ISO 460 grades, making it less complicated and reducing some human errors.   

The Other S Factors

The remaining 4 S factors can also be included in our journey to improve the overall quality of our approach to machinery lubrication. Once we have “Sorted” our lubricants by making sure we have what is necessary, we can move on to “Set these in order.”

In this step, we can ensure that all the types of lubricants are stored in a clean, dry, cool place away from water, direct sunlight, or drastic temperature changes. We can also observe the “FIFO” rules, where the first lubricant that enters the warehouse is also the first to leave and be used in the equipment. Additionally, we can have lists stating the assets in which the assigned oils are to be used and place matching tags on the equipment and dispensing containers to reduce mix-ups of the wrong lubricant being used.

The third “S” talks about “Shine,” which relates to keeping the work area clean. We can also apply this to our oils with the dispensing equipment, making sure we use clean, dedicated dispensing bottles, not the fancy, galvanized, open-top containers where someone showed off their welding skills. Those galvanized containers are huge sources of contamination, which will degrade our lubricants at a faster rate.  

With the fourth “S”, the process of “Standardizing” is used. This was incorporated in the first “S” during our sorting session, where we grouped similar lubricants and standardized them for various applications.

The last “S” is to “Sustain” or make the 5S process a habit. This would involve performing audits every year to ascertain if any new lubricants entered the facility and if they, in turn, should be consolidated with others that perform the same function.  

Benefits of Oil Consolidation  

There are many benefits to the consolidation of lubricants, but here are a few that stand out:

Reduced Cost of Inventory

For warehouses that stock many types of lubricants, there is a cost attached to holding these high stock levels, especially when the lubricants will not be consumed as quickly. However, with a consolidated stock, these levels can deplete at a faster rate than the specialty one or two lubricants, which may be used occasionally by certain assets. This helps to reduce the overall holding cost of the stock.

Reduced Human Error

With lubricants from many different suppliers, it is very easy for someone to get confused and use the wrong lubricant in the wrong application. This can lead to unplanned downtime and a possible flush of the entire system, depending on the level of cross-contamination. However, with a consolidated stock, the risks associated with humans utilizing the wrong lubricant become minimized. 

Reduced HSE Risks

When removing a drum of oil from storage, a forklift may be required (depending on the location). If there were different products from various suppliers, it may be difficult to access the ones needed or may require extra work to remove the additional drums from the other suppliers before the operators gain access to the lubricant they need. With a consolidated stock, it would be easier to access the lubricant needed, and there would be less risk associated with removing it from stock.

There are various types of handling procedures associated with the different lubricants. As such, more procedures will be involved for disposing and handling various oils. This can also increase the HSE risk if someone is not fully aware of how to handle specific lubricants. With a consolidated stock, the HSE personnel will not have as many procedures to be aware of when handling these lubricants.

Reduced Operational Costs

Personnel would no longer be required to handle all the invoicing and payments of several lubricant suppliers for the various brands. This will reduce the hours the accounting department spends on the necessary paperwork and bank transactions for several vendors. Additionally, warehouse personnel will not be tasked with receiving products several times a day from the various suppliers and producing the accompanying paperwork. This can reduce the overall operational costs.

There are many benefits to the consolidation of lubricants, especially in our facilities, but it begins with understanding if we are using them in the correct application or if we’re using an over-specified lubricant in a lower-tiered application. Auditing your facility will assist in making this process easier, as noted above. We all have our role to play in consolidating lubricants to ensure that we have a safer, more efficient plant.   

References

ASQ. (2024, OCtober 19). What are the Five S’s (5S) of Lean. Retrieved from American Society for Quality: https://asq.org/quality-resources/lean/five-s-tutorial

Gears are used in all aspects of life, from bicycles to tiny watch gears, car transmissions, and even highly specialized surgical equipment. Gears keep the world moving. However, when they move, they often rub against each other, and if this friction is not managed, it can cause wear and eventually lead to significant damage or failure. This is where gear oil makes a difference.

In this article, we will explore the various types of gear lubricants, their composition, how they degrade, some storage and handling tips, and what the future holds for these types of oils.

There’s More Than One Type of Gear?

If you’re familiar with gears, you know that despite the standard emoji keyboard, more than one type of gear exists. There are several types of gears, each suited for various applications. As such, each application will have varying environmental conditions, which will require specialized lubricants to reduce friction and wear.

One of the main operational conditions for gears is the transfer of torque. Even when torque is transferred, gears will have sliding and rolling contact, leading to frictional losses and heat generation. Therefore, the lubricants selected for these applications must be able to significantly reduce these frictional losses and cool the gears.

As per (Pirro, Webster, & Daschner, 2016), several types of gears can be classed into three groups based on the interaction of the teeth of these gears and the types of fluid films formed between the areas of contact:

• Spur, Bevel, Helical, Herringbone, and spiral bevel
• Worm gears and
• Hypoid gears

Figure 1 shows some of the types of gears which exist.

It must be noted that hypoid gears transmit motion between nonintersecting shafts at a right angle. Additionally, there is a difference between rolling and sliding.

Rolling indicates continuous movement, whereas sliding varies from a maximum velocity in one direction at the start of the mesh through zero velocity at the pitch line and then back to maximum velocity in the opposite direction at the end of the mesh, as seen in Figure 2.

According to Mang, Bobzin, and Bartels (Industrial Tribology—Tribosystems, Friction, Wear and Surface Engineering, Lubrication, 2011), hypoid gears require heavily loaded lubricants. These should have high oxidation stability, good scuffing, scoring, and wear capacity, as the tooth contacts have a high load.

The lubricant must also have a high viscosity at operating temperature such that the formed film can sufficiently support the load while cooling the gears.

Conversely, hydrodynamic gears such as torque converters, hydrodynamic wet clutches, or retarders require high oxidation stability characteristics but do not need good scuffing or scoring load capacity characteristics. Unlike hypoid gears, hydrodynamic gears experience viscosity-dependent losses, so they must have a lower viscosity at operating temperature.

According to (Mang & Dresel, Lubricants and Lubrication – Second Edition, 2007), there are some frequent failure criteria for gears and transmissions, including:

• Extreme abrasive wear
• Early endurance failure, fatigue of components in the form of micropitting and pitting
• Scuffing and scoring of the friction contact areas

Continuous abrasive wear is usually observed at low circumferential speeds and during mixed and boundary lubrication. Typically, continued wear can cause damage that extends to the middle sector of the tooth flank. Understandably, lubricants with a high viscosity and a balanced quantity of antiwear additives promote a higher tolerance to wear.

Micropitting can be observed on tooth flanks at all speed ranges. Those with rough surfaces are prime candidates for micropitting. Typically, this develops in negative sliding velocities or the slip area below the pitch circle.

Usually, microscopic, minor fatigue fractures occur first, which can lead to further follow-up damage such as pitting, wear, or even tooth fractures. A lubricant with a sufficiently high viscosity and a suitable additive system can help reduce this type of gear fatigue.

At predominantly high or medium circumferential speeds, scuffing and scoring of the tooth flanks occur, and the contacting surfaces can weld together for a short time. Due to the high sliding velocity, this weld usually breaks, causing scuffing and scoring.

Typically, this damage is seen on the corresponding flank areas at the tooth tip and root, which experience high sliding velocity. In this case, lubricants with higher EP (Extreme Pressure) additives can help reduce this damage.

According to (Ludwig Jr & McGuire, March 2019), the type of gear can aid in determining the most appropriate industrial gear oil. The following table is an adaptation from the article:

As per (Mang & Dresel, Lubricants and Lubrication – Second Edition, 2007), transmission gears can be broken down into two main types: those with a constant gear ratio and those with a variable gear ratio. These can be seen in Figures 3 and 4 below.

Gear Oil Characteristics and Naming Systems

From the information covered thus far, we can appreciate that gear oils need to accommodate many changes to their environment. A few characteristics stand out when looking at industrial gear oils (Mang, Bobzin, & Bartels, Industrial Tribology—Tribosystems, Friction, Wear and Surface Engineering, Lubrication, 2011).

These include viscosity-temperature, Fluid Shear Stability, Corrosion and Rust Protection, Oxidation Stability, Demulsibility and Water Separation, Air release, Paint Compatibility, Seal Compatibility, Foaming, Environmental, and Skin Compatibility.

Depending on where you are in the world, you may use a different system to classify gear oils. The ISO Viscosity grade system is used internationally, but the AGMA (American Gear Manufacturer’s Association) system is used in the Americas and some parts of Asia. A chart can be used to move that across these grading systems, as shown below in Figure 5.

As per (Sander, 2020), the AGMA numbers have some particular meanings as stated:

• No additional letters (only a number) – Contains only R&O additives
• EP – Mineral oil with Extreme Pressure additives
• S – Synthetic gear oil
• Comp – Compounded gear oil (3-10% fatty or synthetic fatty oils)
• R – Residual compounds called diluent solvents which reduce the viscosity to make it easier to apply

Another rating that is seen a lot is the CLP rating. This is a German oil standard defined by ASTM DIN 51517-3, in which the test requirements to meet the CLP specification are documented.

This DIN standard covers petroleum-based gear lubricants with additives designed to improve rust protection, oxidation resistance, and EP protection. Some typical classifications seen are CLP-M (which represents mineral gear oil), CLP HC (which represents synthetic oils [SHC, PAO, POE]), and CLP PG (which represents polyglycol PAGs), according to (Santora, 2018).

There are three main DIN 51517 classifications as per (Rensselar February 2013), namely;

• DIN 51517 CGLP – contains additives that protect from corrosion, oxidation, and wear at the mixed friction spots and additives that improve the characteristics of sliding surfaces
• DIN51517-3 CLP – contains additives that protect against corrosion, oxidation, and wear in the mixed friction zone
• DIN 51517-2 CL – contains additives that protect against corrosion and oxidation suitable for average load conditions

The above are some of the more prevalent naming systems for industrial gear oils, and they are found on most gear oils globally.

Degradation

The first set of additives to decrease in gear oils is often the antiwear or extreme pressure additives. This is no surprise, as these oils are subjected to high levels of wear and must withstand extreme pressures. One can also notice a decline in the rust and oxidation additives or even a change in the air release values.

All these properties significantly impact how a gear oil functions. As such, they should be monitored when establishing the health of the oil.

When monitoring the health of these lubricants, some guidelines can be utilized. If there is a change in viscosity of either ±10%, one should look for any other correlating changes.

Typically, if the viscosity increases by 10%, we’re looking at increases in wear metals or the risk of oxidation and development of some deposits in the oil or even contamination of the oil with some water. However, for a decline of 10%, one can expect some form of contamination, typically fuel or another substance which will thin out the lubricant.

The lubricant’s warning levels for wear metals will vary depending on the manufacturer/OEM. However, any consistent rise in wear metals indicates that some component on the inside of the equipment is slowly wearing away.

Gear Oil Storage and Handling

Similar to most oils, gear oils should be stored in a clean and dry space. Often (especially in the past), these gear oils see a settling of the additives to the bottom of the container, indicating a slightly shorter oil life span than other lubricants. However, this is no longer a highly occurring incident with the advancements in additive technology and improved blending practices.

As usual, it is always best to adhere to the OEM’s expiry dates for these products, as different OEMs recommend varying storage times for their products. Generally, synthetic lubricants have an estimated shelf life of 5-10 years, while mineral oils usually last for around 2-3 years, but this is heavily dependent on the OEM and storage conditions.

In some cases, customers tend to store these drums outside in the elements as it makes it easier for them to be readily accessible for decanting into the equipment. However, in these environments, the drums can collect water, which will enter the oil and then, by extension, enter the gearbox. This can cause issues for the equipment and lead to accelerated oil degradation.

Ideally, these oils should be stored in a cool, dry place with ready access to decanting equipment where the decanted oil will not be easily contaminated. Many industrial gearboxes typically require larger quantities of oil, and decanting can take place directly from the drum into the equipment or via a pump.

In these cases, the level of contamination must be minimized by ensuring that the fittings, hoses, etc., are clean and have not been used to decant other types of oils.

The Future of Gear Oils

According to (Industry ARC (Analytics. Research. Consulting), 2024), the global industrial gear oil market size is forecasted to reach USD 5.2 B by 2027. While the Asia-Pacific market holds a significant market share for industrial gear oils in 2021 at around 56.2%, it is interesting that its nearest rival is Europe, at 17.7% or less than ⅓ of its size.

The rise in the Asia Pacific market can be accounted for due to the increase in the rising population and, by extension, the needs of that population and the service sectors they support, including the energy, oil & gas, construction, and steel industries. The figure below depicts the global industrial gear oil market revenue share by Geography for 2021.

From the research conducted by (Industry ARC (Analytics. Research. Consulting), 2024), helical gears appear to be the most popular choice for industrial gears. Interestingly enough, synthetic gear oil held the largest market share and is forecasted to grow by a CAGR of 5.6% for the forecasted period of 2022-2027.

Smaller gearboxes are being manufactured, tasked with outperforming their previous counterparts and producing more torque in a smaller space. With the advent of better, more precise machining tools for gears, there is an increase in the amount of pressure these gears now must handle in smaller spaces.

As such, we will continue to see the rise in the use of synthetic gear lubricants formulated to handle these extreme conditions, as well as more advanced additive packages that can help minimize foaming, reduce oxidation, and aid in the demulsibility of these oils.

References

Industry ARC (Analytics. Research. Consulting). (2024, September 04). Industrial Gear Oils (Mineral & Synthetic) Market – Forecast(2024 – 2030). Retrieved from Industry ARC: https://www.industryarc.com/Report/20008/industrial-gear-oils-mineral-and-synthetic-market.html

Mang, T., & Dresel, W. (2007). Lubricants and Lubrication – Second Edition. Weinheim: WILEY-VCH GmbH & Co. KGaA.

Mang, T., Bobzin, K., & Bartels, T. (2011). Industrial Tribology – Tribosystems, Friction, Wear and Surface Engineering, Lubrication. Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA.

Pirro, D. M., Webster, M., & Daschner, E. (2016). Lubrication Fundamentals – Third Edition, Revised and Expanded. Boca Raton: CRC Press, Taylor & Francis Group.

Rensselar, J. v. (February 2013). Gear oils. Tribology and Lubrication Technology – STLE, 33.

Sander, J. (2020). Putting the simple back into viscosity. Retrieved from Lubrication Engineers: https://lelubricants.com/wp-content/uploads/pdf/news/White%20Papers/simple_viscosity.pdf

Santora, M. (2018, March 20). Tips on properly specifying gear oil. Retrieved from Design World: https://www.designworldonline.com/tips-on-properly-specifying-gear-oil/#:~:text=CLP%20Gear%20Oils&text=Often%2C%20a%20gear%20manufacturer%20will,a%20CLP%20polyglycol%20PAG%20oil