A common misconception about multi-viscosity motor oil such as 5W30 or 0W20 is the "W" means weight. Even in the oil industry we refer to 5W as a 5 weight. The "W" stands for Winter. The first number is the viscosity needed at startup or when the engine is cold. The next number is the viscosity needed at operating temperature. So, a 5W20 needs to act like a 5 viscosity at startup and a 20 viscosity at operating temperature. 5W starts out great but thins out too much as the engine heats up. A 20W is too thick at startup but is right where we want it at operating temperature. Thus, we use a 5W20. We achieve this by using an additive called Viscosity Index Improver which makes the oil thin out less.
Visit our website at www.theautoanalyst.com
