Automobile Lubricants

The main purpose of lubricants in cars is to smoothen the moving parts of the automobile to reduce friction and wear and tear by providing trouble free performance for a longer span of time. A lubricant is a blend of base oils and performance-enhancing additives as required by car engine, gear box and other functional areas.

Engine oil is the most important of the all the lubricants .Lubricants for gasoline and diesel engine are different as the load cycles and fuels are different. Other than reducing friction, the oil in a car engine helps to:

  • Seal the high-pressure combustion gases inside the cylinders
  • Impede the corrosion of metal parts,
  • Absorb some of the harmful by-products of combustion, and
  • 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 at the bottom of the automobile 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 oil also cools these car 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 and tear occurs when a car is first started, before the oil reaches its normal operating pressure and flow.

Diesel Engine Lubricants for Automobiles

The main function of a lubricant for diesel engine is equivalent to a gasoline engine. As the load in diesel engine is much higher it should have adequate anti-wear 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 car 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

The start 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 car sports and used for high performance car s. 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.


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 automobile 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 of the automobile.

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.