When I do an oil change, I always buy 5 quarts of motor oil... I always have 1/2 quart remaining that I never use after... So, what I wan't to know is, do the remaining oil in the quart lose some of it's properties over time since it's been opened for a while (but never put in the engine)? Some of my quarts are over 1 year old... Are they still as good as new oil?

 

I guess the even dumber question is why you're not using the remaining 1/2 quart during the following oil change...

 

Because I tought the remaining oil wasn't as good as the new one after a couple of months and the fact it have been opened...

 

Even if it's been opened, it's better than the stuff that's been in your car for that time.

 

The oil will be fine as long as you keep the lid on tight.

 

If you're paranoid, seal the bottle in a big Ziploc freezer bag. I do this w/ brake fluid bottles after they've been opened.