Lubrication Certifications Review The STLE Certified Lubrication Specialist™ (CLS)

Doug Sackett — Sun, 14 Jun 2026 08:00:22 +0000

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About STLE: A Legacy of Tribology

In 1944, the American Society of Lubrication Engineers (ASLE) was founded as a non-profit association to advance the knowledge and application of the science of lubrication and tribology. The society created a forum for the steel industry, enabling lubrication engineers to build a network of seasoned professionals to interact and grow. In 1987, it was renamed the Society of Tribologists and Lubrication Engineers (STLE) to better reflect its expanding scope across all areas of tribology.

What is Tribology?

Lubrication engineering relates to the reduction of friction and wear between relatively moving parts. The term tribology was coined in the mid-1960s in Great Britain to describe the study of interacting moving surfaces — derived from the Greek word “tribos” (the science of rubbing). Tribology encompasses physics, chemistry, applied mathematics, metallurgy, material science, mechanical engineering, chemical engineering, and applied mechanics.

Origins of the CLS Certification

In 1990, a group of STLE members led by Richard E. Rush, Tom Lantz, Dan McCoy, and Larry Cole formed a committee to create one of the first STLE Certified Lubrication Specialist™ (CLS) exams. The exam was designed for the applied, hands-on individual responsible for keeping industrial machinery operating — with a deliberate emphasis on practical application over theory.

Exam Format and History

The CLS exam was first administered at the 1993 STLE Annual Meeting in Calgary, Alberta. Of the 25 initial candidates, 18 achieved a passing grade. The original format was a fill-in-the-blank exam, requiring test takers to know the body of knowledge thoroughly in order to answer succinctly and accurately.

In 2011, the format shifted to a 100 (150 Question) -question multiple-choice exam — eliminating ambiguity in interpreting correct answers while covering the same 16 areas of field tribology that define the body of knowledge for a certified lubrication specialist.

Exam Integrity and Industry Standing

The validity and integrity of the CLS exam have been challenged over the years. To date, it has passed every challenge — upheld by strict guidelines handed down to all members of the STLE CLS Committee, ensuring the quality of each question and the research and documentation required to support the answers.

The CLS is considered the most extensive certification in the lubrication field and one of the most difficult to achieve. STLE has maintained a long-standing focus on certifying the best, not the masses. The program’s success has inspired other certification programs to emerge in the field — each with its own place in the growth of the lubrication world.

Pursuing the CLS: What to Expect

STLE offers a range of study resources for CLS candidates, including reference materials and recommended reading aligned to the exam’s body of knowledge, along with a curated list of exam prep partners. Connecting with other certified professionals in one’s network is also strongly encouraged — often one of the most valuable parts of the preparation process.

Eligibility is based on a combination of education and relevant work experience. Many candidates are surprised to find they already qualify before beginning formal preparation. Employers are often willing to support the investment once they understand the value it brings: greater technical competence, reduced operational risk, and stronger professional credibility.

The STLE CLS Committee currently comprises 16 subject matter experts from across the industry, continuously updating and reviewing the question bank. Once earned, the CLS designation is valid for three years and renewed through a flexible combination of professional development activities — a process recently revised to better accommodate working professionals.

Key Facts at a Glance

Committee	16 subject matter experts across all exam domains
Languages	English · German · Spanish (available July 1)
Exam Fee	$450 STLE members · $625 non-members
Validity	3 years — renewable via professional development
Learn more	www.stle.org/certifications

Table 1: CLS certification key facts.

The STLE Certification Suite

While the CLS remains the flagship credential in the lubrication world, STLE has developed a broader suite of certifications to serve the full spectrum of tribology and fluid management professionals:

Table 2: STLE Certification Suite

Credential	Full Name	Target Audience
CLS	Certified Lubrication Specialist™	Industrial lubrication professionals — the flagship credential
CMFS	Certified Metalworking Fluids Specialist™	Professionals in metalworking fluid applications
OMA	Certified Oil Monitoring Analyst	Oil analysis & condition monitoring analysts
OMX	Certified Oil Monitoring Expert	Senior practitioners in oil monitoring

Table 2: STLE’s four professional certifications.

Each credential carries its own body of knowledge, exam structure, and eligibility requirements — providing clear, recognized pathways for professionals across all areas of tribology. Together, they reflect STLE’s commitment to setting the standard for professional excellence across the industry.

A Closer Look at Each STLE Certification

All STLE certification exams are taken remotely — at home or in a private work environment — on a computer with a secure internet connection and webcam. Results are provided immediately upon completion. All certifications are valid for three years and require recertification to maintain status. Exam fees are $450 USD for STLE members and $625 USD for non-members (retake: $225/$305 respectively).

CLS — Certified Lubrication Specialist™

The flagship credential — broad lubrication engineering knowledge

The CLS is STLE’s flagship credential and the only independent certification that verifies broad lubrication engineering knowledge for industrial professionals. Recognized globally as the industry standard for technical excellence, independent studies show that CLS-certified professionals earn more, supervise larger staffs, and are more likely to receive raises. The certification is suited for professionals who evaluate and select lubricants, conduct lubrication surveys, develop quality assurance programs, troubleshoot lubrication issues, and maintain lubricant records.

The exam consists of 150 questions in 180 minutes, with a passing score of 70% or higher, and is available in English and German. Prerequisite: 3 years of relevant lubrication experience. Key exam topics include lubrication fundamentals (16%), hydraulics (8%), fluid conditioning and analysis (8%), lubrication programs and consumption (8%), problem solving (8%), grease (6%), bearings (6%), gears (6%), mobile equipment (6%), metalworking (6%), energy (6%), compressors (4%), seals (4%), lubricant manufacturing (4%), and special lubricants (4%).

CMFS — Certified Metalworking Fluids Specialist™

For metalworking fluid management professionals

The CMFS designation verifies knowledge, experience, and education in metalworking fluid management. It is designed for professionals responsible for metal-removal or forming management, application, and handling of metalworking fluids. Target roles include tech support, product application, MWF sales, formulators, product development, and sales representatives. Candidates should have foundational knowledge of fluid chemistry, machining processes, metallurgy, tooling, filtration, and waste treatment.

Prerequisites include a two-year degree in science, manufacturing technology, or business (four-year recommended), plus 20 hours of MWF training and 3 years in a manufacturing setting (or 5 years in a lab). The exam is 150 questions in 180 minutes, 70% passing threshold.

“The certification is highly regarded as an elitist accreditation within the metalworking fluids community. Passing the exam demonstrates one has the necessary training, real world experience and expertise in the field of MWF’s many uses including field analysis, troubleshooting methodology, root cause failure analysis, and refined technical support.”

— Jason Bealby, CMFS Committee Chair

OMA — Certified Oil Monitoring Analyst™

For predictive maintenance professionals overseeing oil analysis programs

The OMA certification is designed for predictive maintenance professionals who oversee oil analysis programs. It suits mechanics, engineers, operators, tradesmen, chemical managers, and on-site lab personnel responsible for oil sampling, reviewing reports, performing the correct tests, and maintaining overall equipment care. The OMA demonstrates proficiency in sampling, data interpretation, and lubricant health assessment to support proactive maintenance strategies.

Prerequisites: 16 hours of oil analysis training and 1 year of experience utilizing oil analysis in the field. The exam covers sampling, application/test methods, data interpretation, troubleshooting, and lubrication fundamentals — 150 questions in 180 minutes, 70% required to pass.

OMX — Oil Monitoring Expert

STLE’s advanced-level oil monitoring credential

The OMX is STLE’s advanced-level oil monitoring credential, recognizing professionals with advanced proficiency in lubricants, lubrication, and comprehensive oil analysis. OMX holders possess the expertise to select appropriate testing techniques, understand sophisticated instrumentation, evaluate complex results to diagnose equipment problems, perform root cause analysis, and prescribe corrective actions. Target roles include oil analysis diagnosticians, lubricant technical support, commercial laboratory technicians, and managers of oil analysis programs.

Prerequisites: 24 hours of oil analysis training and 5+ years of practical experience in oil analysis. The exam is 150 questions in 180 minutes, 70% passing threshold. Key topics include data interpretation (14%), analysis (11%), actions (9%), maintenance (9%), lubricant selection (7%), and limits & alarms (5%), among others.

“The OMX was the most challenging exam I have written among all industry certifications — it represents a proven level of expertise and diagnostic capability in oil analysis.”

— OMX Committee Member

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