Ditto - unlike gasolines (which can do various weird things when mixed), most all motor oils can mix (without problems) with any other motor oil. (Of course, we are talking normally available dino or synthetic 4 stroke oils).

In fact, if you analyze a bottle of Mobil1, you will be surprised at how many different oils are mixed in there.... (And, you will be surprised at how many of them are NOT synthetic, although some are....)

-DavidL