If its regular petroleum bar oil I have used stuff that was easily over 10 years old in a half used, but capped gallon jug. It was stored in an uninsulated shed in the north east. easily saw 90F in the summer to 10F in the winter. I couldn't tell a difference from new stuff. I've used 6 different brands and of those, 2 or 3 different viscosities of quart containers of motor oil. All at least 10 years old, who knows how they were stored, but all were sealed plastic quart containers, I did an oil change with it, and noticed no difference in running/noise/oil consumption and the engine is still going 100k miles later no problems. As for these vegetable based or bio bar oils thats a different matter. When in comes to standard synthetic or regular petroleum based stuff I wouldn't even blink an eye at using really old stuff.