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Motor Oil Shelf Life

I picked up some old motor oil on Freecycle. It had been sitting on a shelf for 20 years. The API grade is ok because my car is 26 years old (SF/CC). Is it still good to use?


Engine oil viscosity is decreased from wear, age in an oxygen rich environment, and from the introduction of impurities, which oil attracts and absorbs and must be filtered.
If you have bought sealed cans of oil, you can use them. The oil in those cans is after all at least 100 million years old. It has no shelf life until you pour it.

I would pour one of them into another oil container and see how much additive has precipitated out. There will likely be what appears to be sand in the bottom of the bottle.

The precipitate will probably wash harmlessly down to your oil pan and go back into solution as the oil is heated and stirred. This is not unusual. I have found precipitated additive in bottles of fresh oil from the store.

If there is a lot of precipitate, and it feels hard when you try to crush it between your fingers, I probably would not use that oil in my car.

Sure, but modern oil would still be better, better performance.

Motor oil is continually improving. The oil, if in sealed cans won’t deteriorate. However,the oil quality has improved over the last 20 years. My brother restored a 1954 Buick very much like the one my Dad owned in the 1950’s and I bought from him in the 1960’s. In the 1950’s we believed that MacMillan ring free oil was the best oil available. My brother uses the oil made today in his 1954 Buick. I’m certain today’s oil is better than the MacMillan oil of the 1950’s. I haven’t even seen MacMillan oil for 45 years. I did find Wolf’s Head oil about 5 years ago, but it turned out to be relabeled Quaker State.

I’m still using oil that I bought in the early 1990s for an older car; no problem and no sediment noted.

For the past couple of years I have been seeing on the internet that older oil with more ZDDP is better for older engines with flat end valve lifters. Modern engines have roller lifters and do not need much ZDDP. ZDDP poisons cat converters. The following web site verifies what I have been seeing. They refer to ZDDP as ZDP.

The site says that ZDDP is coming back but the effect on flat end lifter wear is not yet known.