Motor Oil Additives

Modern quality lubricants are blends of scientifically refined base oils and chemical additives that provide efficient performance for long time periods without excessive deterioration. The function and complexity of additives is constantly growing as engines use new technologies, and the trend for improved additive performance to meet critical demands will no doubt continue to grow.

Additives in high quality finished motor oil perform many functions, such as improving one or more performance properties of the base oil, prolonging the useful life of the oil and reducing deposits and wear. Today’s additives are a must. The following are used to help oil do its basic job:

Oxidation Inhibitors

At high temperatures, even the best mineral oils will, in time, react with oxygen to from sludge, varnish and acids which attach some metals. Additives which slow down the oxidation process are used in modern oils; but these become worn out if oil is used too long.

Corrosion Inhibitors

Water and combustion acids form during operation of every engine, most rapidly when it is cold. The corrosive wear and rusting which they cause can be prevented only by using inhibitors which counteract the acids mixing with the oil film on the cylinder walls or with the oil in the crankcase. These inhibitors are gradually used up; so the acids and other impurities must be removed by changing oil.

Foam Inhibitors

Oil foams when air is churned into it. Anti-foam additives cannot stop this, but they prevent bubble growth and help bubbles quickly break, thus keeping foam at a safe level.


Motor oil detergent-dispersants disperse and suspend sludge and varnish forming materials until they can be removed by draining the oil. As sludge and other contaminants accumulate, these additives will be used up – then harmful deposits form. To prevent this, the oil must be changed.

Anti-Wear Additives

Viscosity and natural friction reducing properties of mineral oils may be insufficient to resist the extreme pressure encountered in modern engines. Therefore, additives are used by refiners to form lubricating films strong enough to carry the loads imposed on them.

Viscosity Index Improvers

An oil which resists thinning when hot, or thickening when cold has a high “VI” or “Viscosity Index.” Chemical additives called “VI” improvers are often used to reduce the rate of oil viscosity change with changing temperatures. It is upon this concept that “multi-grade” lubricants are frequently formulated.

Pour Point Depressants

To make an oil that will flow freely at low temperatures, refiners either remove wax from the oil or manufacture if from crude oils which contain little wax. Pour point depressant additives are commonly used in winter oils to keep them more fluid at low temperatures.

Additives are generally classified by their use or by their particular function. Most additives, while often classified by a single use, are multifunctional. Not all additives are complete improvements, since they may improve certain performance properties, they may also lower others. Furthermore, some additives may be antagonistic to others if used in the same oil. A complete additive system is a very finely balanced part of a high quality lubricant.

NOTE: It is because of this fine balance that the use of other additive, “dopes” or supplements is not recommended. Premium quality lubricants already contain the optimum blend of available additives, scientifically chosen for their effectiveness and compatibility.