Lubricants used in automobiles form a unique class by themselves. They have to perform in different types of vehicles under a wide variety of operating conditions. In the last two decades, the design, efficiency and manufacture of automotive vehicles have undergone a radical change all over the world. This resulted in a variety of vehicles, both petrol and diesel, which are modern, fuel efficient, comfortable and high performers. These vehicles would have fount it difficult to operate without progressive advancements in lubricants performance standards.

Performance standards for Automotive lubricating oils are established by numerous bodies around the world. In USA, the Society of Automotive Engineers (SAE), the American Petroleum Institute (API) and US military, issue lubricant specifications which are very popular and internationally accepted. 

In India Lubricant specifications are issued by the Bureau of Indian Standards, which are generally in line with the above International standards.

LUBRICATION REQUIREMENT OF INTERNAL COMBUSTION ENGINES

Internal combustion engines are two types. Four stroke or Two stroke, petrol and diesel engines. Petrol engines are spark ignited and Diesel engines are of compression ignition type. Depending on the type of engine, methods employed for lubrication vary considerably.

FOUR STROKE ENGINES

For four stroke engines the arrangement most widely applied is pressure circulating system for the main and big end bearings, with a by-pass to the camshafts and other components. Cylinders are lubricated by oil thrown from the big ends, by direct feed from mechanical lubricators, or by a combination of two. Gudgeon pins are lubricated by means of oil leads taken from the big ends or by oil throw. These arrangements apply both to wet and dry sump systems, the former being usually employed in engines of the high speed type, whereas the latter are used for large stationary sets and normally incorporate an oil cooler.

Notable exceptions to these generalizations are horizontal engines of the open-crankcase type and vertical two-stroke crank case compression scavenging engines, both of which usually have ring oiled main bearings and banjo feed to the big end.