It's sold under the names of Valvoline, Havoline, Mobile One, Pennzoil, Amsoil, Castrol GTX, Quaker State, and Motorcraft. They also have a listing on the container that might read something like; SAE 30, SAE 40, 10W-40, 10W-30, 5W-40, 5W-30, 0W-30 or 0W-40. Those listings are the grades of oil. The SAE 30 grade is considered single-grade oil and 10W-30 would be considered multi-grade oil. The grade of oil is a measurement of viscosity that the oil provides and the "W" represents that it's acceptable for use during the wintertime. .
Viscosity is defined as resistance of a liquid to sheer forces. The viscosity of oil is a very important in protection of your engine. A lower number in reference of viscosity of oil means the oil is of a lighter weight and it will also flow more easily than a higher number of viscosity would. The lighter weight fluid is easier for the engine oil pump to circulate the oil throughout the engine. This also provides lower oil pressure to the engine but it also provides a greater volume of oil than if a heaver weight of oil was to be used. Heavier weight oils also create more heat in the engine due to the oil pump having to work harder to force the thicker oil throughout the engine. These heavier oils are used in racing engines due to the higher temperatures and the higher speeds these engines typically encounter. The thickness of the oil clings to the metal surfaces more readily than lighter oil would when the engine is being raced hard. A 20w-50 viscosity is commonly used in racing.
There are two different grades of oil available for your automobile engine. Single-grade oil will only flow at one specific viscosity and is becoming obsolete due to the multigrade oils broad range of protection. Multigrade oil begins with an oil base such as SAE 10 and certain polymers are added to the oil to extend its range of viscosity to a 10w-40 grade of oil. This means this oil can flow like 10W oil at lower temperatures and flow like a 40W at higher temperatures.
