FI Flyer

About five years ago, I bought a quart of Mobil One 0-40 oil for my new Cayman S. Since it was hard to find, I thought it would be wise to keep a quart in my car just in case. I never used it. Now that I have a new car that requires the same oil, I wonder whether this ancient oil is still good or whether I should replace it with something newer.

I assume that oil is basically immune to aging but I wonder about the additives and, perhaps also, whatever magic makes regular oil into synthetic.

Can someone with a better understanding of the chemistry of synthetic oil and its additives please explain and advise me what to do?

Fahrer

I am sure the oil is OK. There are additives in the oil to protect it under extreme conditions for an extended period of time. Compared to normal operating conditions it is as if your oil was stored in a deep freeze. I would not hesitate to use.

alexb76

Only thing could be moisture getting into oil, but if it was sealed may not be as much of an issue. Also, I am not sure how old Oil is on the shelf when you buy one.

BostonDuce

Your only risk for using "old" oil (out of sealed containers), is the API requirement for your car has eclipsed the API rating on the old oil.

Since you haven't changed cars it should be fine.

BD

LlBr

IMHO? Use it in your lawnmower. Get a new quart. Why? Because I don't trust any mfgrs.. Formulations are changing all the time to increase profit and they do not have to inform the consumer. The oil is probably the same but you never know. What's the risk and what's the benefit? Related issue: I had some BMW oil from 2000. Was gonna use it in my newer Bimmer. Why not? It literally said "BMW High Performance Synthetic" on the lable and was the correct viscosity. I happened to ask the service tech when I was there and he said, "No! Don't use it." Not the same as your case but still, it's easy to screw up it seems.