Additives Used in Lubricating Oil | Additives in Oil.

Additives used on lubricating oil are not merely marketing gimmicks; they play a crucial role in ensuring your vehicle’s engine operates at its best. Various kinds of additives used in lubricating oil are discussed in this article.

Additives Used in Lubricating Oil

Additives Used in Lubricating Oil

Any mineral oil, by itself, does not have all the properties described in the previous article. Desired properties, certain additives are mixed in the oil during the manufacturing process.
Additives are specialized compounds blended into engine oil to enhance its properties and provide extra benefits. These compounds are carefully selected to target specific issues that arise during engine operation. From reducing friction to cleaning deposits and neutralizing harmful acids, additives work tirelessly to keep the engine in top shape.
These additives are as follows- 

Viscosity Index Improver

The Society of Automotive Engineers(SAE) rates oil viscosity in two different ways: for winter and for other than winter. Winter-grade oils are tested at 0 degrees and 210 degrees Fahrenheit. There are three grades-
  1. SAE 5W,
  2. SAE 10W,
  3. SAE 20 W.


The “W” indicates water grade. For other than water use, the grades are SAE 20, SAE 30, SAE 40, and SAE 50, all without the “W” suffix. Some oil has multiple ratings, which means they are equivalent, in viscosity to several single rating oils.
For example, SAE 10W and 30W oil is comparable to SAE 10W, SAE 20W, and SAE 30 oils. 

Pour point depressants

Some oils become so thick at low temperatures that they will not pour at all. Certain additives can be put into the oil which will lower the temperature to a point at which all the oil becomes too thin to flow. Such additives keep the oil fluid at low temperatures for adequate engine lubrication during cold weather starting and initial operation. 

Oxidation Inhibitors

At high temperatures, when oil is agitated with or sprayed into the air in the crankcase the oil oxidation takes place. When the oil is oxidized, it breaks down to form various harmful substances, which coat the engine part with an extremely sticky, tarlike material. This may clog oil channels and tend to restrict the action of piston rings and valves. Oil oxidation may produce corrosive materials also in the oil, that will corrode bearings and other surfaces. Certain chemicals, known as oxidation inhibitors are added to the lubricating oil to resist oxidation.

Corrosion Inhibitors

Corrosion inhibitors are added to the oil to inhibit corrosion due to the formation of acids at high temperatures. Also, rust inhibitors are added which displace water from metal surfaces so that oil coats them. 

Rust Inhibitors

In churning action, the engine crankcase tends to cause the engine oil to foam. As the oil foams up, it tends to overflow or to be lost through the crankcase ventilator. Also, the foaming oil is not able to provide normal lubrication of bearings and other moving parts.
Foaming oil in hydraulic valve lifters will cause them to function poorly, work noisely and wear rapidly. To prevent foaming, anti-foaming additives are mixed with the oil. 

Foam Inhibitors

To prevent or slow down the formation of deposits of carbon, gum, and dirt, some engine oils are certain detergent additives. The detergent acts much like ordinary hand soap in the oil to loosen and detach the deposits. The oil then carries the loosened material away. The larger particles drop to the bottom of the crankcase, but smaller particles tend to remain suspended in the oil. These impurities are flushed out when the oil is changed.

Detergent dispersants

A dispersant is also added to the oil to prevent the particles from clotting and to keep them in a finely divided state. Without dispersant, the small particles will tend to form large particles which might block the oil filter and oil passages.

Extreme Pressure Agents

An automotive engine may subject the lubricating oil to very high pressure in bearings and valve trains. To prevent the oil from squeezing out, extreme pressure additives are put into the oil. They react chemically with metal surfaces to form very strong, thin, and slippery films. Thus, they help the oil by providing protection during moments of extreme pressure. 


From maintaining the right viscosity to combating wear and tear, each additive serves a specific purpose. The careful formulation of these additives enhances engine performance, prolongs engine life, and reduces the risk of breakdowns and costly repairs.
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