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Viscosity
Technically speaking, viscosity (or SAE grade) is a measure of a fluid's resistance to flow. Bear in mind that during normal engine operation, oil circulates several times around the circuit every minute, hence the importance of viscosity. In the case of motor oil, viscosity is indicated in two ways (or two grades), the cold grade, also known as dynamic viscosity, and the hot grade, also known as kinematic viscosity.
Cold grade oil
The cold grade is a number followed by the letter W, while the second number indicates the hot grade. The cold grade gives an indication of the oil's ability to start the engine and prime the oil pump when ...
