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I have 3 quarts Mobil 1 sitting in the garage from 2006 from a beemer that drank oil. The oil was never opened but exposed to 100 degree summers.
Think it is still good for a mower, edger, go cart or something?
Somehow I just knew that there would be disagreement on this question...LOL Standard forum answer is to do whatever is more expensive.
If the manufacturer says not to use after 5 years, why would you? Blending oil requires heat and other process, when it gets old and starts to separate, just shaking it up does not make it blend back together.
When I retired, I went to work for a performance oil company and I found out things that I never wanted to know, such as this.