The manufacturers say 4 years, most of the additives start to fall out of suspension and cannot be re-added. People have used old oil and have not had problems but sometimes things do go wrong. In aviation, 4 years from both Shell and Phillips, expiration date is on the box. Had a seminar on oils and the shell engineer explained what happens when oils and the additives separated. It may not harm a beater but I would not use old oil in anything of value or something that is hard to replace. I don't have a dog in this fight but that is what the literature says. Tim
I don't believe this and proven it wrong many times with several different brands of oil.
I am not saying I would put 20 year old oil in a airplane, but I would and have into cars and trucks many times with excellent protection.
I rebuild lots of my own motors so I have seen it with my own eyes, not hear say.
Even Budweiser stopped putting expiration/born on dates on there beer. lol
