Oil question time vs use??

Dirty Dawg · Apr 20, 2009

I have always had trouble getting this clarified. I know oil questions tend to end in some kind of argument, but here goes.

Does oil have a limited shelf life? Does it degrade in a motor that is not being used over a period of time, say two years, or does it only degrade thru use?

Thanks Ike

a70eliminator · Apr 20, 2009

Re: Oil question time vs use??

I don't think motor oil degrades from sitting in a crankcase. some refigerant oils I know have an affinity for moisture and become contanimated, but with motor oil I wouldn't think it's an issue

meesh · Apr 20, 2009

Re: Oil question time vs use??

Oil does not get old, but it can be contaminated from condensation from sitting in a stored motor. Also it does break down from use, dirt and heat.

WizeOne · Apr 20, 2009

Re: Oil question time vs use??

Oil, in an engine, does not degrade with time beyond this fact. Most petroleum oils have a sulfer content. When moisture (condensation) combines with the oil it forms sulfuric acid. Sulfuric acid does more harm to motor components than wear from normal operation. This is one of the reasons that oil change recomendations are of such short duration.

Synthetics, on the other hand, have zero sulfer content, so until you pass the point of additive breakdown or dirt load, you are good to go for long periods of time. Otherwise time does not affect moisture load or dirt. Once an engine gets to operating temperature, any moisture is burned off and/or any emulsion from moisture combining with oil is filtered out.

Don S · Apr 20, 2009

Re: Oil question time vs use??

Mercruiser and Volvo recommendation is change the oil and filter yearly or 100 hours, whichever comes first.

Now if you are talking about oil in an engine sitting out behind the barn for the past 10 years, yeah, it probably has some sludge and moisture in the bottom of the pan from condensation.

Now if you are talking oil setting on a shelf at Wallyworld or your Local Merc dealer, then don'w worry about the shelf life...... Might get concerned when the container is over 50 years old.

Dirty Dawg · Apr 20, 2009

Re: Oil question time vs use??

Thanks all, this was really not meant for the boat but my Harley. Changed the oil last year and for various reasons, never got to ride the bike. I was debating if I should change out the oil this year or leave it as is. I debated if oil broke down over time, even if not in use. Of course time can vary for people,but I pegged it at approx. two years. Thanks all Ike

Silvertip · Apr 20, 2009

Re: Oil question time vs use??

How much oil does a Harley take? Hardly a major investment either way so why not change it and not have to worry about it. While boats and cars do vastly different types of service, my car has an oil life monitor and it signals oil change intervals based on lots of parameters including, speed, ambient temperature, engine temperature, idle time, etc. To test this feature, I've gone 6000 miles and it said I still had 20% life remaining. In this country we have been way to accustomed to 2-3000 mile oil changes. Europeans run primarily synthetic oil and 6000 mile oil change intervals is pretty normal and those vehicles, in Germany for example, spend lots of time at or near triple digit speeds.

Don S · Apr 20, 2009