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"Does engine oil get old and go bad?"

Madison Sully

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Funny guy.

I am in the habit of 10,000 mile oil change intervals on my cars. PTW, more like 6,000 miles, weather and season dependent to some degree.
As far as shelf life, yeah, never gone far enough to consider it, personally.
 

670cc

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I’ve often wondered if new engine oil has a limited shelf life, but having NEVER seen an expiration date on a bottle of engine oil, I treat it as if it lasts indefinitely in the bottle, or in an engine where it has seen little or no run time.

Even if expiration dates were to begin appearing on oil bottles, I’d be skeptical as to whether it really expired, or if the oil company just hopes you’ll throw it out and buy more for their own profit.
 

Junkie

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I've been told that some acidity develops from combustion byproducts, so if it's going to sit for a long time it's a good idea to change first.
 

Jt105

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I’ve often wondered if new engine oil has a limited shelf life, but having NEVER seen an expiration date on a bottle of engine oil, I treat it as if it lasts indefinitely in the bottle, or in an engine where it has seen little or no run time.

Even if expiration dates were to begin appearing on oil bottles, I’d be skeptical as to whether it really expired, or if the oil company just hopes you’ll throw it out and buy more for their own profit.

I could understand an open bottle of oil going bad from oxidation. I’m not worried about it though. I figure that it would take multiple years for oxidation to have any measurable effect. Any leftover oil in an open bottle gets used at the next oil change.

JT
 

Madison Sully

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I've been told that some acidity develops from combustion byproducts, so if it's going to sit for a long time it's a good idea to change first.

If it ran a long time and was subject to all those combustion byproducts, then yes there may be an acidity of the oil. But motor oils have bases in them to neutralize those combustion byproducts, measured by TBN (Total Base Number). Point being, if it's time to replace your oil based on the reduction of TBN, it's just time to change your oil. It's not due to time passing.
 

Junkie

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Right, but if you're near there and going to let it sit for a couple years, it's probably a better idea to change before rather than after
 
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