While there are other nuances to motor oil classifications that need to be understood before changing or topping off the oil in your car’s engine, one of the first things to address is the viscosity, or weight, of the oil your engine requires. In the late 1970s, when I first started working on cars and doing engine maintenance, 10W-30 was about the only multi-viscosity oil on the market. Advertisement
Today, all of the best motor oil brands make a variety of multi-viscosity motor oils to satisfy the requirements specified by automakers….

Check out the original article: [Slashgear]Can You Use 5W-30 Engine Oil Instead Of 5W-20?