Lubricants- engine and its oil

The main purpose of lubricants is to lubricate moving parts of the vehicle to reduce friction and wear and tear by providing smoothing, trouble free performance for increased length of time.

A lubricant is a blend of base oils and performance enhancing additives as required by engine, gear box and other application areas. At the refinery, the crude oil is refined into gasoline, diesel, kerosene, LPG, naphtha and base stocks (Lube). This base stock is further processed, blended and strengthened with required properties to make different kind of lubricants.

Of the all the lubricants engine oil is the most import. Lubricants for gasoline and diesel engine are different as the load, cycles and fuels are different. The oil in an engine does more than just reduce friction between its moving parts. It also helps to seal the high-pressure combustion gases inside the cylinders, to impede the corrosion of metal parts, to absorb some of the harmful by-products of combustion, and to transfer heat from one part of the engine to another.

Combustion of rich air-fuel mixture during starting, idling and warm up form deposits. These deposits in the form of varnish, sludge, soot and carbon, interfere with proper engine operation.

The engine oil keeps all the deposit forming material in suspension and gets rid of them by oil filter, or draining out at proper intervals.

Engine oil is stored in the oil pan or sump at the bottom of the engine. A pump forces the oil through a filter and then through a series of passages and galleries to lubricate the engine’s moving parts. The flow of also cools these parts. Rapidly moving engine parts actually float on a thin film of oil and never make contact with one another. This is called hydrodynamic lubrication and usually begins when an engine reaches the idle speed. Most engine wear occurs when a cold engine is first started, before the oil reaches its normal operating pressure and flow.


Diesel Engine Lubricating Oil

The main function of lubricant for diesel engine is the same as mentioned for gasoline engine. As the load in diesel engine is much higher it should have adequate antiwear properties. Diesel fuel contains a high level of Sulphur which burns to form oxides of sulphur , which in turn in the presence of water, form sulphur acids resting in high corrosion of engine parts. Hence the need of alkalinity reserve in the oil which is represented by its TBN or Total Base Number. Generally, the higher TBN value more the alkalinity reserve or acid neutralizing capacity the oil contains.

Synthetic Oil

T The advent of synthetic oil more than fifty years back opened up vastly improved and new alternative lubricant to mineral oil. But being very expensive, it is confirmed to the arcane world of motor sports and used for high performance cars. They are also widely used in developing countries for a number of reasons like improved overall engine performance, low oil consumption, long drain periods, less engine wear, improved engine cleanliness and faster starting. Taking into consideration the price tag and its efficacy, the option is left for consumer’s discretion.

Additives- what they do

Plain mineral oils cannot provide all the necessary functional properties that an engine requires. These plain mineral oils need fortification with chemicals/additives which when used in small quantities, import or enhance the desirable functional properties. Some of the types and reasons for their use are as follows:


Dispersants: Keeps sludge, carbon and other deposit- precursors suspended in oil.

Detergents: Keeps the engine parts clean from deposits.

Rust/Corrosion Inhibitors: Prevents or controls oxidation of oil, formation of varnish, sludge and corrosive compounds, limit viscosity increase.

Extreme Pressure (EP), Anti wear and friction modifiers: These form protective film on the engine parts and reduce wear and tear.

Metal deactivators: Forms surface films so that metal surface does not catalyze oil oxidation.

Pour Point Depressant: Lowers freezing point of oils assuring free flow at lower temperatures.

Anti-foamants: Reduces foam in crankcase and blending.

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