Mechanical Engineering - Automobile Engineering - Discussion

Society of automotive engineers.

The numbers 20W50 refer to the viscosity of the motor oil, set by the Society of American Engineers. This refers to its fluidity or thickness. The "20W" indicates how quickly the engine will start when cold or in cold weather. The "50" refers to the thickness of the oil when the motor has been running for a while.

What is multi grade oil?

A quality of oil that can use in every weather for the purpose of engine lubrication, it may be cold or hot atmospheric temperature.

What are meaning of SAE 30, API SF, SAE 20 W-50, API 50 ?

Multi-grade oil is oil that has viscosity modifier additives in it. These additives allow the oil to flow differently under cold and hot conditions. Multi-grade, or multi-weight oil is designated with two numbers. The first one is followed by the letter "W".

This first number indicates the viscosity (weight) of the oil in Winter (cold) , and the second number indicates the viscosity (weight) of the oil under normal engine temperature (hot). It is important for the oil to be thin enough to flow easily when cold. This protects the engine parts from undue wear in cold starting conditions.

Oil viscosity in winter condition is tested up to -18 C and hot up to 99 C.

API stands for the American Petroleum Institute.

SAE stands for the society of automobile engineer's. The multi-grade oil is which can be used in different conditions. The W stands for winter. This means the oil is suitable for both cold and hot conditions.

Thanks for the answer @Anuraj.