Does oil age if opened but not used?

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I put fresh oil in a lawnmower about two years ago and it has sat unused since. Does the oil need to be replaced even though the engine was not started once? I know there may be some water condensed in there but when I start it up again won't it just burn off in 30 minutes or so? Does anything else occur to degrade the oil if it is not used but is exposed to air that can't be burned off next time it is run? Can I run it this year with the old but unused oil or should I put in a fresh quart before I start using it?
 
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Originally Posted By: Quattro Pete
If it was a car, I'd say change it, but since it's just a mower, I'd say run it.


+1. There are some mowers that people never change the oil in. You'd be ok to run that oil for this season then dump it in fall. Just make sure the oil is at a safe level on the dipstick.
 
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Maybe it oxidized a bit, but then again it hasn't been hot.

Considering most people never change the oil in their mower for 5+ years I think you will be okay. Flip side is, it takes 10 minutes to change. I would just go with whatever makes you feel better. If you took the time to question it, you will probably mentally feel better changing it.
 
I've asked Mobil technical support years ago if Mobil 1 would have a shelf life in the bottle. I got a humorous response that the bottle would probably disintegrate before the oil went bad.

That being said, if you read Mobil's warranty terms, they only consider it valid if the oil is used in a vehicle less than five years after purchase.
 
As long as it is not milky due to water contamination it should be fine to run. I fixed up a motorcycle that sat for 25 years and it had milky oil due to water but i wouldn't think that would happen in a couple years of being stored inside.
 
I remember reading here in motor oil 101 that oil gets permanently thicker as it is exposed to cold weather and as such oil should not be stored in a garage that is not climate controlled. I do that now. I always have an extra quart of the mazda oil for my car and as I do rotate stock when I buy more oil, I keep that extra quart under the kitchen sink.

I wouldnt hesitate to use garage oil in my lawnmower though.
 
It's still fresh oil it hasn't been contaminated enough to start oxidation at any sort of measurable rate.

The fact that air cooled mowers get really hot will ensure any water is burned off very quickly.

I would be more worried about the gas.
 
Originally Posted By: y_p_w
I've asked Mobil technical support years ago if Mobil 1 would have a shelf life in the bottle. I got a humorous response that the bottle would probably disintegrate before the oil went bad.


I believe it. This guy ran five years (but only 1780 miles) in his pickup, then did UOA: https://bobistheoilguy.com/forums/ubbthreads.php/topics/4190879/1992_Surburban_Big_Block_-_M1_

To the OP: Do whatever lets you sleep at night. My garage is heated; about 55 degrees in winter when it is in the teens outside. Lawnmower has never been cold enough for condensation in the oil.

I bought a new lawn mower in 2004; changed the oil in 2005 and the old oil looked like honey. Haven't changed it since 2005 and it is still translucent and not black. Top it up now & then. Of course, I run Amsoil full synthetic signature series, which is the best oil in the world.
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Yeah, I would just run the oil you have in it.




Originally Posted By: JC1
There are some mowers that people never change the oil in.

Some of the new Craftsman mowers specifically say "Never change the oil, just check and add"

I think that's crazy though...
 
Did the cap get put back on ... It's somewhat about exposure to ambient humidity. Water changes oil chemistry slowly. Personally, I would just run it and not think twice
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The motor does have a simple vent system for crankcase vapors to exit and it can let in a small amount of air, but the exchange rate is minute ...
 
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I run my mower oil for a season (50-100 hrs total) and it always comes out black. This time I have Mobil 1 in it.

Even if the oil is 10 yrs old and has been stored in a constant temp above freezing....just shake it and go.
 
I kind of question whether there is some 'vapor' instilled in a jug of oil. You know, like with milk, it can be good for weeks or months, but as soon as you break the seal it must be refrigerated and used within a week or so.
 
Originally Posted By: mjoekingz28
I kind of question whether there is some 'vapor' instilled in a jug of oil. You know, like with milk, it can be good for weeks or months, but as soon as you break the seal it must be refrigerated and used within a week or so.

Regular pasteurized milk can't take that, but ultra-pasteurized milk can. It has an off taste in my opinion. Then there's shelf-stable milk.

I've seen some odd things in my day including CO2 injected into my beer growler to keep it from going flat, or Motul brake fluid that's claimed to be injected with nitrogen to keep it from oxidizing or suffering water vapor issues.
 
You know what I mean y p w. Coke is good for ages, then you pop the top and its flat in hours.

A can of corn would probably be good for decades, but you disturb the seal and the race is on.




Yes, I discovered some Great Value milk recently that is about double the price- but the expiration was like two months later instead of the 'normal' two weeks for regular milk. Then there is milk in a can or box that is not cooled.



Potato chips seem different because they can probably go stale even if unopened. But opened if kept folded and a chip clip they never seem to deteriorate.







I guess the oil could have picked up a minute amount of contaminants from being in the sump or even mixed with the oil that didn't drain out. In my vehicles I try to keep oil no more than a year in the sump. But if you never started it, I would regard being in the sump just as good as being in the bottle!
 
To be honest I don't remember if I changed the oil first then ran the engine dry or ran the engine dry first then changed the oil. It has been in an outside shed and has seen from -10F to 90F over a year or two.
Without a strong response otherwise I will just inspect it to see if it looks like normal fresh oil and run it for the season then.
I just remember a mechanic once told me to change a car's oil (conventional) at least twice a year no matter what the mileage.
 
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