Mixing oil types

Saskatoon, SK, Canada
I know all us us on this board check to see if the Castrol 0W30 is GC, or not. And I know up here, we don't have to worry anymore due to the fact I believe all the Castrol 0W30 is now GC, and it's everywhere. Hmmm maybe I should buy 1000 bottles and sell on e-bay lol. But wondering for all the people out there who buy half GC and half Group 3 North American 0W30 if it will be bad for car, and if Castrol should be in trouble for having in exact same container, when their chemistries seem so far apart.