10 years from manufacture if in quart bottles. Should have a use by date or a manufacture date on the bottle and you should be able to go from there.
Good Luck,
Mahlon
I bought a case of Aeroshell W80 today and the "Use By" date was stamped on the case. It was 4 years from the date of manufacture. If it were my precious engine, I would use that 10 y.o. oil in my lawn mower. I'm funny that way...