What do the SAE ratings on motor oil mean?
SAE ratings on motor oil have to do with the viscosity of the
oil. The viscosity is the oil's resistance to flow, or an oil's
speed of flow as measured through a device known as a viscometer.
The higher the SAE, the thicker the oil and the slower it will
flow.
Oils that have a number like 5W30 or 10W30 have been tested at a
colder temperature. These oils will flow at the fist number's rate
at colder temperatures and the second number's rate at higher
temperatures.
SAE means Society of Automotive Engineers