Viscosity is a measure of a fluid’s resistance to flow. For motor oils, the lower the viscosity, the thinner the oil. 5w30 and 5w20 are two common motor oil viscosities. The “5w” in both cases refers to the oil’s viscosity at low temperatures. The “30” and “20” refer to the oil’s viscosity at high temperatures. 5w30 oil is thicker than 5w20 oil at high temperatures. This means that 5w30 oil will provide more protection for your engine at high temperatures. However, 5w20 oil is thinner than 5w30 oil at low temperatures. This means that 5w20 oil will flow more easily through your engine at low temperatures.
Whether you should use 5w30 or 5w20 oil in your engine depends on a number of factors, including the climate in which you live, the type of driving you do, and the age of your engine. If you live in a cold climate, you may want to use 5w20 oil because it will flow more easily through your engine at low temperatures. If you do a lot of hard driving, you may want to use 5w30 oil because it will provide more protection for your engine at high temperatures. If you have an older engine, you may want to use 5w30 oil because it will help to seal any leaks.