Myths about Engine Oil (Source: Fleet Street Journal)

Myth #1

Oil is oil:

Engine oils are far more than a refined petroleum product. They include a complex balance of additives that do things such as keeping soot dispersed in the oil, neutralizing acid produced by the combustion process, maintaining proper viscosity and protecting engine surfaces from wear and corrosion. Engine oils for your truck should meet standards set by the American Society for Testing and Materials, denoted on the oil in the API "donut." The current standard is CI-4. To meet this standard, oils must pass a battery of tests. Engine makers also have their own tests such as the Mack EO-N standard.

Myth #2

You can tell something about the quality of an oil by looking at a pressure gauge:

Seeing the oil gauge rise after changing to a new oil is not always a good indicator of whether an oil is good or not. High pressure can mean that the oil isn't flowing well. Pressure detection devices on engines are not sensitive enough to distinguish between the minor differences in oils.

Myth #3

You can tell the condition of your oil by looking at it:

Don't think that black oil is a bad thing. All diesel engine oils turn dark within minutes of entering the engine. If an oil is doing its job, it is dispersing the soot and keeping it suspended in the oil. Because of that the oil turns black. the only way to really assess your oil is through used oil analysis.