[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