Engine oil shelf life

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Dec 13, 2002
North Carolina
I'm not the brightest person in the world but help me understand shelf life with engine oil.

So if I took a vergin oil sample of say Mobil 1 and kept the rest of that quart for 20 years and then took another sample of it the readings would be way different? To the point that the oil would no longer be useable? What exactly goes bad with the oil? Does the additive package seperate from the base stock?

I'm just trying to understand this. Been reading on here a few posts about oil that someone has seen and is old stuff and then someone else posts that they wouldn't use it due to its age.

If that is the case then the 3 quarts of Penzoil SAE 30 HD that my father has in his garage that he has been useing in the lawn mowers isn't any good anymore since it is over 14 years old. Correct?

There has got to be a reason. I understand what shelf life is. Here in the Air Force we have it on the packings and rubber O-rings and other seals we have on hand to use when we rebuild our Central Gear Box's and Jet Fuel Starters that go in the F-15E. They carry a 2 year shelf life and we have to rotate our stock if we don't make it through them in that time frame. But usually that doesn't happen because we use up everything we have in a few months time and order more.

Thanks for any and all help with my understanding of this.
You have to consider that in 20 yrs there would most likely be no vehicles were the oils spec's would be suitable for. What good would a qt of SA rated oil be good for today?

If the oil is in a sealed container, it will last a very long time. If the seal is broken, then its likely it won't last very long exposed to moisture and air, even if just from the short time you have the container open. That would hold true for most fluids, once open you use them up in a reasonable time period, say 1 max.
There have been many posts on the subject. Go to search and do a title search on shelf.

[ September 05, 2003, 08:31 AM: Message edited by: Al ]

Originally posted by Mike:
If the seal is broken, then its likely it won't last very long exposed to moisture and air, even if just from the short time you have the container open.

I doubt this is true at all. Oil is not hydroscopic as brake fluid is, nor will the presence of water, per se, in motor oil affect its chemical composition. In the sump, motor oil is exposed to condensation on cooldown, but it's the partially oxidized combustion products and fuel supplied sulfer blowby products that result in acid buildup. Even at that, UOAs typically show less than 0.05% unless there's an overt cooling system leak. In the real world, unused motor oil in a sealed container is consdidered stable at ambient temperatures indefinitely. At least that's what the blenders' material safety data sheets say that I've researched online. In use, our car owner's manuals suggest a range of a minimum of 3,000 miles/3 months up to 10,000 miles/12 months. This is petroleum oil or synthetic oil, people, not fresh produce or meat set out to rot in the hot sun. The basic stuff is the end byproduct of ancient animal and vegetable material putrifaction. Besides air, dirt, and rocks, what else has survived intact several million years? (Well, except for my ex-mother-in-law...)

[ September 05, 2003, 09:07 PM: Message edited by: Ray H ]
I think 14 year old oil in sealed containers would be just fine to use. The idea of the S or C rating being out of date should not matter. Surley I would not want to poison the converter in my new car with an SF oil but the same oil would be just fine in my old truck.

Bottom line I guess is that I would use the oil as long as it has not been opened.


Originally posted by Rat407:
Does the additive package seperate from the base stock?
It Can. It will, to what % - I donno, they will vary.
I have just got rid (have a few tubes left)
of some test tubes with oil samples from 20 years ago, In fact I'm testing a grease right now from that batch in a wheel bering.
I placed varied OILS in tubes and corked them and left them upright through all my moves the last 18-20 Years. Results vary, but they all (even the best although slight) settled-out. A couple looked like a LUGGIE at the bottom some looked like milk, they were not the same, but they did settle out.

-snip- wouldn't use it due to its age.
Up to you, maybe if it's filtered ???
pour some in a glass and check the bottom of the bottle, and tell us your findings.


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