Is it cool to mix 0w-30 and 5W-30 Mobil1 synthetics. I would assume it is, but I heard something about 0W-30 having polymer in it that gives it its 0W-30 characteristics. I don't want to dilute the polmer additive if it is critical to performance. Any thoughts on this anyone. I just want to use up all of my old "extra" bottles of oil that get left behind because I buy oil by the case, which is about 1.5 bottles too much!

 

You won't harm the engine by doing this. If you use mostly 5W-30 and 1.5 bottles of 0W-30 the oil will just behave mostly like a 5W-30. If you want 5W-30, use 5W-30. If you don't want to give up the properties of the 0W-30, use it instead.

 

You'll be fine .