Does Engine Oil Expire??
 

I have about half-a dozen quarts of Valvoline Racing 20-50 oil sitting on the shelf that was bought back in 1999. Brand new still sealed. I opened one just to see if anything's changed compare to new ones I recently bought. Still clean and clear. only difference is the color has darkened to more brownish instead of the golden yellow. Viscosity seems to feel the same.

Does anyone know if that's useable? I can't find expiration date on the bottle. I was told engine oil don't expire, but i'm skeptical to use them. Thanks

When I was in A&P school, years ago there was some discussion of additives (detergents, film modifiers, etc) possibly precipitating out from extreme long term storage, but this was decades ago and concerned early multi-vis aviation oils.

What I bet you're seeing is discoloration caused by UV exposure and/ or the oil being discolored by the plastic of the container is made from.

I'd pour a bottle of it into a quart jar, then cut the bottom off the oil bottle and look for deposits. No significant deposits, then it should be fine.
I have used oils that were 20+ years old, but they came out of paperboard or metal containers.

Lastly? When in doubt, throw it out. Oil is cheaper than the engine. Just because I'd dump 20 year old Castrol into my Bonneville does not mean I'd advise you do the same.

that's great news

i sacrificed a bottle by dumping it out in a clean pan after i wrote this post and there were no deposits or anything weird other than the discoloration. Also after consulting w/ my old automechanics teacher, he also said it was fine to use them.

thanks for the reply

I've read that if conventional oil is stored outside and is repeatedly subjected to freezing temps, waxes can form.

Oil is cheaper than an engine.