A somewhat technical oil question

[smockers83]

I was thinking about this for some reason the other day while I was driving. People always say an idling engine is hard on the oil while at the same time, at cruising speed, the engine is running at the same speed over a long period of time, essentially idling. So wouldn't this be just as hard on the oil or is there something else to it?

[joe603]

I'm not sure who says that an idling engine is hard on oil...it's not. The only thing hard on oil is heat. Now a car that idles for extended periods of time can lead to deposits on the valves (in diesels its called wetstacking and is a common problem with power generator engines that don't have enough load)

So to answer your question, no it's not hard on the oil when you're cruising. However, cruising at the same RPM for extended periods can cause problems on a new engine and should be avoided until it's broken in.

[smockers83]

Gotcha. Maybe that's what was the point, the deposits on the valves. There was some argument that I read that it was hard on the oil for some sort of reason and I remembered it the other day and thought I'd ask. Thanks Joe.