Mixing oils of different brands

[ltsnotme]

So I have a couple of quarts of Castrol GTX left from the last oil change, and I just happened to get a gallon of Quaker State brand (same viscosity, both are API service SN). Are there any reasons I shouldn't mix the two?

[Towncivilian]

No problem at all. Theoretically, "additive clash" is possible, but street oils do not suffer from this and do not have any issues mixing with other oils. Oil is mixed any time you change brands, anyway, as some residual oil is always left over in the engine obviously. I wouldn't do it all the time, of course, but to get rid of some extra quarts laying around once in a while? Go for it!

[ltsnotme]

Yeah, that's what I thought too, thanks.