I did my oil change and ended up using less than 4.5 quarts.. since this Mobil 1 stuff is relatively expensive is it ok to keep that half quart and use it next oil change? If it's better to just get rid of it and buy another 5 (unopened) quarts I'll do that.. but just wanted to know what you guys do.

Thanks!

I save my 1/2 quart for the next time.

I also document the activity with a couple of digital pictures that show the odometer and the oil & filter that I've put in and I keep receipts for the supplies. I figure if I ever have an engine warranty issue at least I'll have something to indicate that the oil was changed.

I'm using the Toyota brand zero weight oil. It's only available in quart containers from the dealer. I also have the leftover at each change. I simply keep it to add if needed. I can also use it for the next oil change. I doubt it hurts to keep it as long as the cap is on tight.