The second car that I ever owned was a 2002 Chevy Silverado 2500 with a 6.6L Duramax diesel engine under the hood. It wasn't my first choice, but it was a hand-me-down from my father after my 1993 ...

To help the oil keep your engine cool, calm, collected — and clean and corrosion-free — refiners blend in various additives, which can account for as much as 25 percent of the cost of the oil.

Motor oils also have different classifications that mandate what age of engine it's best used in. According to the United States Department of Energy, this is also called the API (American ...

Motor oil includes additives developed to reduce changes in viscosity because of temperature. Certain motor oils are designed to be thinner (less viscous) when cold and more viscous (thicker) when hot ...

It may also recommend different oil depending on whether you live in a hot or cold climate. The most important thing is to use oil that's the right thickness, or viscosity, for your car's engine.

For example, motor oils labeled 10W-40 had viscosity measures that were widely and unacceptably at variance with the universally defined characteristics of 10W-40 motor oil.

"This motor oil is not suitable for use in most gasoline powered automotive engines built after 1930," Lee said, reading the fine print on one bottle. "And I don't know about you.