An Introduction to Lubricants and Lubricant additives for Engineers by Professor Ashlie Martini

Title:
Introduction to Liquid Lubricants: Fundamentals, Additives, and Future Challenges

Introduction
Liquid lubricants are a cornerstone of tribology, essential for reducing friction, minimizing wear, and ensuring the reliable operation of mechanical systems. In a recent TriboNet webinar
, Professor Ashlie Martini, Chair of Mechanical Engineering at the University of California Merced and leader of the Martini Research Group, delivered an accessible introduction to the composition and function of lubricants. Her talk was designed for a broad tribology audience, ranging from mechanical engineers to researchers, and addressed both fundamentals and emerging challenges such as electrification and sustainability.

The Basics: Composition and Functions of Lubricants

At their core, lubricants are composed of base oils and additives. In the case of greases, a thickener is also added to create a semi-solid structure.

Functions of lubricants: separating surfaces, dissipating heat, and transporting contaminants away from contact zones.

Base oils:

Mineral oils – widely used, cost-effective.

Synthetic oils – offer superior performance in extreme conditions.

Biological oils – emerging as sustainable alternatives.

Additives: tailored to improve performance, including:

Viscosity modifiers (temperature stability).

Oxidation inhibitors (extended lubricant life).

Boundary additives such as friction modifiers, anti-wear, and extreme pressure (EP) agents.

Thickeners in greases: act like a sponge, holding and releasing oil under heat and shear.

👉 Related reading: Lubricants and Additives

Classification Systems: Making Sense of Lubricants

Professor Martini highlighted widely accepted standards that help engineers and researchers compare and specify lubricants:

API base oil groups – classification by refining method and performance.

SAE viscosity grades – common in automotive applications.

ISO viscosity grades – used in industrial settings.

Viscosity Index (VI): indicates how much viscosity changes with temperature.

These classifications form the backbone of lubricant selection, ensuring the right balance of cost, performance, and application-specific needs.

👉 Related reading: Viscosity in Tribology

Emerging Trends in Lubricants

Tribology is not static, and neither are lubricants. Professor Martini emphasized several important trends:

Sustainable lubricants – growing research into biological oils and eco-friendly additives.

Electric vehicle lubrication – EVs change the performance priorities of lubricants, with increasing focus on lubricated-for-life systems, electrical conductivity, and thermal management.

Green additives – replacing traditional but regulated chemicals like ZDDP with environmentally friendly alternatives.

👉 Related reading: Tribology in Electric Vehicles

Practical Insights and Quotes

Professor Martini’s ability to explain complex chemistry in simple terms stood out. A few memorable quotes include:

“The goal … is to introduce liquid lubricants focused on composition and function in a way that’s accessible to ologists at any level.”

“In an ideal world, perhaps we would all be using silicon and fluorine containing base oils, but in many cases a mineral oil is just good enough.”

“It’s an exciting and challenging time for the lubricants field.”

Her Q&A session also addressed real-world concerns such as mixing additives, selecting greases for high temperatures, and the role of lubricants in the EV era.

👉 Related reading: Grease in Tribology

About the Speaker

Professor Ashlie Martini is the Mon Lane and Robert Bryant Presidential Shell Chair in Excellence in Engineering at UC Merced. As Chair of Mechanical Engineering, she leads the Martini Research Group, known for its cutting-edge work in tribology. With a mechanical engineering background, she bridges the gap between chemistry-heavy lubricant science and the practical needs of engineers.