Running Hot...oil that is, good or bad?

[beiland]

I was cruising thru Popular Science mag just recently and ran across this 'invention award' for the Over7, "a system that by redirecting and then heating an engine's oil cuts gas consumption by 7% and emissions by up to 30 percent"

www.popsci.com/diy/article/2012-05/higher-efficiency-lower-emission-engine-system]2012

I'll bet this sparks some debate

[foggysail]

I don't know about engines but I do know that my ancient Ford Econovan came standard from Ford with a transmission oil cooler.

[gjordan]

Colder oil has much more friction than oil at the proper temperature. The question is "what is proper temp". Max oil temp is usually stated in an operators manual, but normal operating temp may or may not be listed. I suspect that raw water cooled engines could gain some milage if there oil ran at a higher temp, but fresh water cooled engines almost always have an oil cooler in the system that keeps the oil from getting too hot. What most people dont realize is that when at start up the oil cooler actually heats the oil up to operating temp quicker than if there was not an oil cooler. The oil cooler or heat exchanger uses the fresh water part of the system to keep the oil temp stable. When you are first running an engine the coolent water gets up to temp before the oil does, so the heat exchanger transfers that heat to the oil to bring it up to normal. This cuts down on friction and wear on the engine, which makes your engine run better and last longer. I am sure someone can give a clearer explanation than this._____Grant.

[leftbrainstuff]

The primary function of your oil is to support a compressive load to stop parts with relative motion from touching. (minimise wear)

Ideally you want this to occur with minimum shear forces on the oil. (minimum friction)

Most oils can only achieve this within a small temperature difference. (20 - 30 degrees)