Is there an "in engine" shelf life for used oil?

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I remember reading oil can age and get acidic if used even for a short while, driven only a thousand or so miles. I have 2 cars, a sports car using a synthetic Mobil 1 oil which I drive about 1-2 thousand miles yearly when there is no salt on the road and a small truck with a gas engine which I use dino oil (Rotella) as recommended by another forum to prolong tappet longevity which is driven about the same amount.

Would it be more optimal to change the oil yearly prior to putting the car/truck away so each engine will have fresh oil while they sit for 6 months?
 
I think an oil change before storage is only minimally better. And if you make it a point of driving your car 20 miles or more right before storage, it really doesn't matter if your oil has 1,000....2,000...or 3,000 miles on it. I put 1200 miles on my car annually. I change the oil in later May...to get the freshest oil in there for hotter summer driving. The oil has 800-1000 miles on it by winter time. That doesn't bother me. The Mobil 1 is probably good for 3-5 years and 5K-10K miles....but I change annually any ways. I'm more concerned about maintaining my car's low mileage engine than saving $20 per year....at least for now. Maybe in the future I'll go to 2-3 yr OCI's.

Now if you're prone to parking your car with short trips on it, or turning the engine over in winter w/o driving it 10-20 miles? Yeah, then I'd want the freshest oil in it prior to whenever the most "short trips" would occur. And idling the engine in the garage is the shortest trip possible.

The TBN of a quality oil will tend to last by mileage...not time. One exception might be excessive fuel dilution from a poorly functioning fuel delivery system. Short vs long trips and summer/winter driving factor into how quickly contaminants build up (ie TBN depletion).
 
Originally Posted By: ymc226
I remember reading oil can age and get acidic if used even for a short while, driven only a thousand or so miles. I have 2 cars, a sports car using a synthetic Mobil 1 oil which I drive about 1-2 thousand miles yearly when there is no salt on the road and a small truck with a gas engine which I use dino oil (Rotella) as recommended by another forum to prolong tappet longevity which is driven about the same amount.

Would it be more optimal to change the oil yearly prior to putting the car/truck away so each engine will have fresh oil while they sit for 6 months?



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My jeep just got an oil change, lost track of how many years it's been in there, I think the last OC was in 2014 sometime.
Really, how much acid can build up without introduction of oxidants? I'm sure there is a dip in TBN from it, but doubt it would be a full point. Check back in a half a dozen years when I do a UOA on the Jeep
lol.gif
 
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