The purpose of engine oil is to form a film of lubrication between all
moving parts of an internal combustion engine to reduce friction and wear.
Choosing the right engine oil for your vehicle and changing the oil during
regularly-scheduled maintenance intervals will keep the engine running
smoothly over time. The recommended oil type and specification for your
vehicle can be found in the owner's manual. Another place to find it is on
the oil fill cap. it will be based on the ambient temperature where you
live. There are two engine oil codes that the owner’s manual will specify,
an APl and an SAE.
API Code
All oil has an APl code which stands for American Petroleum Institute. it's
a service rating for the quality, cleanliness, and types of detergents in
the oil. The code will always be two letters.
SAE
The SAE is the viscosity or thickness of the oil. Modern oil is
multi-viscosity oil. The SAE may be something to the effect of 5W-30. The
first number-letter combo (5W) indicates the viscosity or thickness of the
oil when it is cold. The second number is the viscosity at the engine
operating temperature. Before they had multi-viscosity oil there was only
single-viscosity oil (such as SAE 30), which in cold weather was extremely
thick. Trying to pour it into your engine would be like pouring honey, but
more importantly, it would be hard to pump the oil and lubricate the engine.
That's why older engines had to be warmed up before you could drive them.
