german castrol 0w-30

[aaron0558]

I know here we go again with the oil Q's but I need to ask. I'm about to change own oil b/c I really don't know what's coming out of the gun at the dealer. From what I've read the m1 0w-40 and gc 0w-30 have similiar operating temperature thicknesses, the 40 on the thin side and the 30 on the thick side. Being they're both 0 weight at start up is one thicker/thinner than the other? Is the gc 0w-30 safe to use for chicago summers b/c I'm really not sure if I want to bounce b/t oil brands. Any negative comments about the gc 0w-30?? thank you!!