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does motor oil break down over time with little mileage or engine hours?

I have a 2010 Silverado with less than 3500 miles and is now a year old. On Star says I need to change the the oil now. Is it really needed? I also have a tractor with low hours and the oil is several years old (same type question).


  • Yes, the GM oil life monitor puts the various factors in to estimate oil life. I'd follow it. And 'several years' is too long for me. Once a year is my maximum time. What does the tractor owners manual say.
  • edited July 2011
    It's not a question of the oil breaking down in 3,500 miles/1 year.
    Instead it is a matter of the oil likely being diluted by water vapor (a normal byproduct of combustion), as well as the potential for oil sludging to take place.

    The problem with a vehicle that logs only 3,500 miles in 1 year is that--in most cases--those miles are accumulated mostly with short-distance local driving. That type of driving does not allow the engine and the oil to become hot enough to evaporate the water vapor, and the oil becomes diluted over time.

    The process of dilution of the oil, coupled with an engine running on a richer than normal mixture when it is not fully warmed-up, can create the perfect storm for the formation of sludge, internal corrosion, and resulting engine damage.

    Normally, I don't trust the automated oil life monitors on cars to tell me when to change the oil, but in this case, I would suggest that you take its notification very seriously. Even if you are skeptical of an oil change being necessary at this point, the reality that you will void the warranty on your engine by failing to change the oil on the recommended schedule should prod you into action.
  • If you look in your owner's manual you will see that GM advises an oil change when the monitor specifies and at least once per year. I can't say how oil in your little used engine deteriorates but once per year is a tolerable expense. If you made only a few long trips to total 3500 miles, your oil might be ok and you could stretch the change interval to two years. The small savings, however, is not worth encountering the possibility of subtracting from the far end of your engine's lifespan.

  • No, oil does not break down just by sitting in your crankcase. But you have been given a number of reasons favoring an annual oil change nevertheless. A change may not be totally necessary at this time but it is a sensible precaution.

  • It's unanimous. It should be changed.

    As others said, the oil itself doesn't technically "break down", but there are very good reasons to change it anyway.

    I'd change the tractor oil annually too. Engines......and tractors......are expensive. Oil is cheap. Oil is an engine's lifeblood. Kept fresh it can do a much better job.
  • I agree with all of the above.
  • I used to have a car that I drove about the same 3,500 miles per year as you. I changed its oil once a year, despite the fact that the specified oil change interval, in miles, was 7,500.

    I don't agree that oil should be changed every six months on low mileage vehicles, but I can't see leaving it unchanged for more than a year. The reasons why have already been listed by others.
  • My mechanic for our low-mileage classic says the oil should be changed at least every six months any time after the car is driven, since some of the additives added by the manufacturer will probably be less effective after six months once they are exposed to engine operating stresses. Modern oils are quite good and it's not like the oil is going to suddenly change into mush after six months, but you are stacking the odds in your favor, and an oil change is relatively inexpensive.
    Unlike modern oil, modern ethanol-based fuel is worse than it used to be and that may be even more of a problem for cars which are not driven very often.
  • edited July 2011
    I drive my car about 4000 miles a year. Driven 2-3 times a week
    The Operator's Manual says change the oil every 6 months or 5000 miles.
    So I change it every 6 months.
    However, I change the oil filter once a year.
    I don't think water and unburned fuel get trapped in the filter.
  • Motor Oil seldom if ever "breaks down"...It's very stable and retains its properties for a long time. What happens to Motor Oil is that it becomes CONTAMINATED with the by-products of combustion..This contamination can lead to sludging and the corrosion of internal engine parts..

    While Motor Oil is no longer cheap, it's still a lot cheaper than rebuilding engines...
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