Helping dad clean up and organize around the farm, I've discovered a trove of filters and oils.

The oil containers were "stored" inside but exposed to temperature fluctuations. The jugs have "expiration" dates on them, many are 8-15 years old. Expiration dates or "sell by" dates on food mean nothing to me. Unless it stinks or is fuzzy I'll eat it. I've even been known to eat around the moldy spots...

Knowing that the dates that apply to food are mainly for marketing purposes, is motor and gear oil the same? Reading on-line, the industry seems to think that oils should be used within five years or it suffers from breakdown, separation, additives degrade etc. After finding the first couple gallons I thought I'd just run it in my old 318ci gasser since it already leaks and burns oil anyway. I don't want to subject my beloved engines to inferior oil but I also don't have enough engines with oil bath air cleaners to use up gallons and gallons. I could add to the tractor fuel but still, it would take decades. I could recycle it but I just hate the thought of recycling like 25 gallons of "brand new" oil.

I'm talking Valvoline Extreme and Rotella etc that looks and smells ok with no signs of seperation or precipitating, but is long past the expiration dates...

 

I would find it unlikely that oil would breakdown in a unopened jug stored away from high heat and sunlight.

 

This question has crossed my mind in the past too. Also wondered that if oil does deteriorate in some ways in time, is the rate of deterioration any different between dino oil and synthetic?

 

I'm wondering this too, but I don't think the oil is going bad.

 

It depends.

Sometimes I'll use it up on a less fussy application. Like old ATF - I wont trust It in an auto trans, but i figure its fine in basic chain drive transfer case. Old engine oil - for a pump'n'dump/flush sort of thing, sure. Otherwise, cutting into my diesel fuel supply gets it gone.