testing the limits of oil endurance

[Dom Ferris]

With the economy in its fragile state and oil prices at stratospheric levels some people are wondering just where the upper service limit is really located in terms of changing your oil? Some companies sample the oil and have it analyzed for contaminants and properties to determine whether to change the oil or wait. They say oil degradation depends more on patterns of use than mileage and/or time.

Most of us cannot get access to fleet rates for chemical analysis of oil or coolant chemistry. Nonetheless, we read the engine owner's manual or call engine manufactures or Newell Coach etc and are told numbers like 15,000 miles and 12 months as a basis for an oil change. Why 12 months if the mileage is only 5,000 miles for that given year? Why not 24 months? Why not 30 months? What happens to gallons of oil when it is just sitting there in a sealed engine instead of a sealed plastic jug? How long can it sit in a plastic jug before it is not usable? 60 months, 20 years?

I don't have a clue. I'm reluctant to exceed the mileage limits but what about the time limits? It's a benign environment compared to some applications because we never even start the engine unless we are leaving on a trip.

It's not the end of the world to change the oil, for instance, but multiply the gallons wasted by a few million RVs and it's a huge amount of oil that might not need to be changed for a while.

Am I alone in wondering about this? Is anyone testing the limits of oil endurance and learning which variables really matter?

Dom

[ccjohnson]

My philosophy has always been; I can buy an awful lot of oil with the +/- 25K it takes to replace an engine if damaged due to penny pinching oil & service costs just once.

[NewellCrazy]

I am not going to try to answer your question since I'm not a lubrication engineer. Oil does not wear out but there are other factors which determine the interval for changing oil such as operating conditions, climate, how hard the engine is worked and length of trips etc.. as CCJohnson put it "I can buy an awful lot of oil with the +/- 25K it takes to replace an engine"

[Vantare]

Contaminants and moisture accumulates in the oil in the crankcase (not in the jug), leading to time-based recommendations for a change. Chances are the oil is still good at 12 months or more, but it takes an oil analysis to prove it. An analysis isn't real expensive (about $25), but for many of us it's just as easy and cost effective to go ahead and change the oil.

[Will Procter]

Do an oil analysis at your regular change interval before actually changing the oil. If the oil tests good, then go another thousand or two and do the same thing until you find the interval that you need based upon your vehicles duty cycle. You may find that you can easily double your current interval. Lots of stop and go city driving is considered heavy duty service and requires more frequent changes. Continuous highway driving is less severe.