My dad has been asking me about the advisibilty of going up a grade in his truck. He has the 5.3 ecotec3 and GM is pretty clear that 0w-20 is the only recommended grade. However he is interested because he tows a lot in running 5w-30 instead. Because the truck has VVT, cylinder deactivation, and a variable speed oil pump I'm not sure how to advise. Has anyone done this? Warranty is not a primary concern. The plan is to keep the truck forever.