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What are Lubricants?

A lubricant is a substance applied between surfaces in motion to reduce friction.

Lubricants are a part of your daily life whether you realize it or not. For your car to function, for products to be delivered to shelves and for crops to be harvested lubricants are a necessity. Almost all mechanical equipment requires lubricants to keep moving parts moving and to reduce the amount of downtime or maintenance. Nearly every product you see was developed with the help of lubricants, from silverware to servers lubricants play a fundamental role in manufacturing. Even the power you use to light and heat your home would be unavailable without the gear oils used to lubricate power plants and generators.



The range of lubricants is diverse, some examples include: motor oil, gear oil, transmission fluid, metalworking fluids, greases and food grade lubricants. Lubricants come in both liquid and solid states. Some properties that are specific to lubricants are viscosity, film strength, load capacity and oxidation resistance.

Viscosity is the lubricant’s resistance to flow. A higher viscosity, or thicker lubricant, is necessary in heavy duty or slow speed applications to ensure the lubricant stays in place, while in light load or high speed applications a lower viscosity, thinner lubricant, is essential to avoid clogging or lubricant loss. 

Film Strength measures the capacity of the lubricating film created to separate two parts that may be in contact. Film strength is determined by the lubricants viscosity, load capacity, operating speed, or temperature of the application.

Lubricants must be able to withstand all of the force generated in an given application. The measure of this is the lubricant’s load carrying capacity. Using the correct lubricant for an application will form a durable film that withstands all of the forces generated during operation.

Oxidation resistance is a lubricant’s ability to resist the formation of sludge, varnish or acids when in high temperature conditions or exposed to air. Choosing a lubricant with the correct oxidation resistance will extend the performance and lubrication period of the equipment.

Operating conditions will change dependent on application and industry. The lubricants effectiveness is often determined largely by the operating conditions and environment. Any extreme conditions will warrant a specialized lubricant that can withstand the high temperature, pressure or corrosiveness of that environment. 


API Classifications

A lubricant is formulated with base oils, additives and thickeners. Generally, between 35-100% of a lubricant is base oil and 0-65% is comprised of additives. The American Petroleum Institute (API) has organized base oil types into 5 groups dependent on their composition and characteristics.

Group I & II

Group I and II are mineral oils that are refined from crude oil. Group I base oils are the least refined and generally have a low viscosity index. Group II base oils are more refined and have a higher viscosity index. This provides improved oxidation stability, performance and thermal resistance.

Group III

Group III base oils are also paraffinic mineral oils, but are made using a more complex process. Group III’s are more refined and produces an even higher quality oil with excellent oxidation stability, low-temperature properties and performance characteristics. Although it is a mineral oil, most countries consider Group III to be synthetic.

Group IV

Group IV base oils are known as polyalphaolefins. These fully synthetic base oils are chemically engineered to provide excellent performance characteristics, including: an ability to maintain viscosity over a wider temperature range, improved thermal stability, oxidation resistance, and low-temp fluidity. 

Group V

Group V base oils encompass all oils that don’t fit into the other categories. Many Group V products are synthetic and can include additional oils used as additives to increase performance. Group V base oils are used in highly specialized applications that require specific properties.


Understanding the importance of lubricants and their impact on the efficiency and longevity of mechanical systems will pay dividends in discussions with customers.