ICML vs STLE vs NLGI: Which Lubrication Certification Is Right for Your Maintenance Team?

If you are trying to build a more capable lubrication team and you’ve started researching certifications, you’ve probably encountered three main options: ICML, STLE, and NLGI. They are not competing alternatives — they serve different roles at different career stages. This guide explains what each credential covers, who it’s designed for, and how to choose the right starting point for your team.

Newton Industrial Solutions technicians hold certifications from both ICML and STLE — the two most widely recognized professional credentials in industrial lubrication and reliability. Our lubrication training programs prepare candidates for all major credentials through our online platform at lubricant.training and through onsite training at client facilities across South Carolina, North Carolina, and Georgia.

ICML Machinery-focused · MLT + MLA series · most widely held

STLE Engineering-focused · CLS · broader tribology scope

NLGI Grease-specific · CLG · narrow but deep focus

The Three Main Lubrication Certification Bodies

ICML — International Council for Machinery Lubrication

The International Council for Machinery Lubrication (ICML) offers the most widely held lubrication certifications in industrial maintenance. ICML certifications focus specifically on machinery lubrication — the practical knowledge and skills needed to correctly apply, select, store, and analyze lubricants in industrial equipment.

ICML offers two main certification tracks:

• MLT — Machine Lubrication Technician (Level I and II) — for hands-on maintenance technicians
• MLA — Machine Lubrication Analyst (Levels I, II, and III) — for reliability engineers and oil analysis specialists
• LAT — Lubrication Apprentice Technician — new entry-level credential introduced in 2026 with no prerequisites

STLE — Society of Tribologists and Lubrication Engineers

The Society of Tribologists and Lubrication Engineers (STLE) offers the Certified Lubrication Specialist (CLS) designation and the Oil Monitoring Analyst (OMA) credentials. STLE certifications cover a broader scope than ICML — including tribology (the science of friction, wear, and lubrication), lubrication engineering principles, and the full spectrum of lubricant chemistry and application.

• CLS — Certified Lubrication Specialist — the broadest and most rigorous lubrication engineering credential
• OMA I and OMA II — Oil Monitoring Analyst — condition monitoring and oil analysis specialists

NLGI — National Lubricating Grease Institute

The National Lubricating Grease Institute offers the Certified Lubrication Specialist — Grease (CLG) credential. Unlike ICML and STLE credentials, which cover the full spectrum of industrial lubrication, the NLGI CLG is grease-specific — covering grease chemistry, manufacturing, testing, and application in depth. It is highly valued in grease manufacturing and in applications where grease is the primary or only lubricant used.

Side-by-Side Comparison

Factor	ICML MLT I	ICML MLA I	STLE CLS	NLGI CLG
Focus area	Machinery lubrication practice	Oil analysis & reliability	Tribology + lubrication engineering	Grease technology
Best for	Maintenance technicians	Reliability engineers	Senior engineers/managers	Grease specialists
Prerequisites	None	MLT I recommended	2 years experience	Industry experience
Exam format	Multiple choice	Multiple choice	Multiple choice	Multiple choice
Study time required	40–80 hours	60–100 hours	100–150 hours	60–100 hours
Renewal period	5 years	5 years	3 years	3 years
Industry recognition	Very high — most widely held	Very high	High — engineering focus	Moderate — niche
Recommended path	Start here	Second certification	Senior credential	Grease-heavy environments

Which Certification Should Your Team Start With?

Maintenance Technicians — Start with ICML MLT I

For maintenance technicians with hands-on lubrication responsibilities, ICML MLT I (Machine Lubrication Technician Level I) is the universally recommended starting point. It covers all fundamental competencies — lubricant selection, storage, application methods, contamination control, and basic oil analysis — in a format designed for technicians rather than engineers.

MLT I can typically be prepared for in 40 to 80 hours of focused study. Candidates with basic mechanical maintenance experience often prepare in less time. After MLT I, MLT II is the natural next step — covering more advanced topics including relubrication interval calculations, bearing lubrication theory, and lubrication program design.

Reliability Engineers — Start with ICML MLA I

For reliability engineers and maintenance engineers who work with oil analysis, condition monitoring, and predictive maintenance programs, ICML MLA I (Machine Lubrication Analyst Level I) provides the analytical foundation. MLA I covers lubricant sampling, oil analysis test methods, result interpretation, and condition monitoring program management — the knowledge base for running a meaningful oil analysis program.

MLA I pairs naturally with Newton Industrial Solutions’ oil analysis programs — an engineer with MLA I credentials can interpret oil analysis results, manage the program, and act on findings without depending entirely on external expertise.

Senior Engineers and Managers — STLE CLS

The STLE CLS (Certified Lubrication Specialist) is the broadest and most rigorous lubrication credential available. It covers tribology, lubricant chemistry, additive systems, fluid power, metalworking fluids, and environmental considerations — well beyond the machinery focus of ICML credentials. CLS is particularly valued in engineering management, reliability management, and technical sales roles where broad theoretical knowledge is important alongside practical expertise.

Grease-Intensive Environments — Consider NLGI CLG

For plants where grease is the dominant lubricant — automotive component manufacturing, mining, heavy construction equipment — the NLGI CLG provides deep expertise in grease technology that neither ICML nor STLE credentials fully cover. It is best pursued after ICML MLT credentials, not instead of them.

Recommended Certification Path by Role

Role	Year 1	Year 2–3	Year 3+
Maintenance Technician	ICML MLT I	ICML MLT II	STLE CLS (optional)
Lubrication Technician	ICML MLT I	ICML MLT II	NLGI CLG (if grease-heavy)
Reliability Engineer	ICML MLA I	ICML MLA II	STLE CLS
Maintenance Supervisor	ICML MLT I	STLE CLS	ICML MLA I
Plant Manager / Engineer	STLE CLS	ICML MLA I	ICML MLA II

How to Prepare — Study Resources and Training

Preparation for ICML and STLE certifications requires structured study against the exam body of knowledge. Newton Industrial Solutions offers certification preparation training through our online platform at lubricant.training — covering the full ICML and STLE exam curricula with structured modules, knowledge checks, and practice questions. Our platform is available 24/7 on any device, making it practical for maintenance technicians studying around shift schedules.

For teams of four or more, our onsite lubrication training programs deliver structured sessions tailored to your specific equipment, lubricants, and operational environment — combining certification preparation with hands-on practical application.

What Certified Technicians Can Do That Uncertified Technicians Cannot

• Calculate correct relubrication intervals from bearing geometry and operating conditions — not guess from a calendar
• Identify grease thickener incompatibility before mixing products that will damage bearings
• Interpret oil analysis results and distinguish normal wear from developing failure
• Recognize over-greasing signs before they cause bearing failures — not after
• Design a lubrication route that ensures no bearing is missed and no bearing is over-lubricated
• Select the correct lubricant for a new or replacement piece of equipment without calling a distributor rep

Key Takeaways

• ICML MLT I is the right starting point for most maintenance technicians — no prerequisites, 40–80 hours of study, covers all fundamental competencies
• ICML MLA I is the right starting point for reliability engineers focused on oil analysis and condition monitoring
• STLE CLS is the senior credential for engineers and managers who need broader tribology and lubrication engineering knowledge
• NLGI CLG is a specialist credential for grease-intensive environments — best pursued after ICML credentials
• Online preparation at training covers ICML and STLE exam bodies of knowledge — self-paced, any device

Ready to Start Your Team’s Lubrication Certification Journey?

Newton Industrial Solutions provides ICML and STLE certification preparation through our online platform at lubricant.training and through onsite lubrication training programs at client facilities across South Carolina, North Carolina, and Georgia. Our instructors are ICML certified and STLE certified — the same credentials your team will be working toward.

Online Training: lubricant.training

Call: 864-432-3510

Email: info@newtoninds.com