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Composition of an Engine Oil

News - What is the composition of an engine oil?


Mineral, synthetic or semi-synthetic, what are engine oils composed of?  Let’s take a closer look at what goes into this essential lubricant, and what role do the additives perform.

Composition of mineral, synthetic and semi-synthetic oil

When we discuss about the composition of engine oils, it is essential for us to know that every engine oil is made of a base oil and additives. Since, mineral, synthetic and semi-synthetic oils have different viscosities, roles and uses, their compositions are different from each other. The base oil is generally either refined crude petroleum, or polymers synthesized in the laboratory.

What are mineral engine oils made of?

Mineral engine oils are natural oils derived from crude petroleum. After being extracted and conveyed to a refinery, these oils undergo several refining processes to remove impurities. Mineral oils mainly consist of hydrocarbons (oxygenated or non-oxygenated), but it may also contain traces of compounds such as sulphur or nitrogen. After mineral oils are processed, additives are added to them to improve performance.

What are synthetic engine oils made of?

Synthetic engine oils can be created chemically in the laboratory, but it can also come from refined petroleum. Refining synthetic oil is a more complex process than for mineral oil, as it involves modifying the structure of the hydrocarbon molecules. The processes for obtaining the oil ensure that only the best molecules are retained. Many additives are also added in the process. Synthetic oils are considered high-end oils that deliver higher performance.

Why are additives added to engine oils?

Additives ensure the quality, performance and lifespan of engine oils are in place. Both mineral oils and synthetic oils have additives added to them.

There are many kinds of additives and their roles differ from one and other:

1) Oxidation inhibitor additives
Engine oils are changed regularly because with time they tend to oxidise and lubricate engine parts less effectively. Oxidation inhibitor additives are added to engine oils to slow this process and improve the lifespan of an engine oil. 

2) Detergent additives
Just like the name, detergent additives help keep the hot areas of the engine free of deposits and neutralize acids that form in the oil. 

3) Dispersant additives
Dispersants work hand in hand with detergents to keep engines clean. The main use of dispersants is to keep contaminants away from the oil and minimise the damage.

4) Anti-foaming additives
Detergent additives at times generate foam that enters the surface of the oil. This will restrict engine oils from performing well. Anti- foaming additives manage the foam produced and in turn save your engine. 

5) Anti- wear additives
Anti- wear additives add a layer of protective solid oil to prevent metal-to-metal contact. Like the name suggests, these additives reduce the friction and wear of engine parts. These additives are mostly used in mineral oils. 

6) Corrosion inhibitor additives
They prevent corrosion and rusting of metal parts of the engine. 

7) Viscosity index modifiers
These polymer additives prevent oils from thinning in different temperatures. 

8) Antifreeze additives 
These additives let the engine oils adapt to different temperatures. They increase the fluidity of cold oils as they tend to thicken otherwise.