I'll go out on a limb and say that if the OM specs 5W-30 it will also say to use 10W-30 for summer and synthetic 5W-30 or 0W-30 for winter. GM truck OM have been like that for some time.
The OP resides in Louisiana. No issue using 10W-30 year-round. 10W or not, it's still a M1 synthetic. The oil will not cause an engine failure; the warranty is moot at this point anyway. If tested, the oil would pass that weak dexos certification.
There is no reason whatsoever to not use this excellent oil in this application.
Originally Posted By: NH73
2011 and 85000 miles, its probably out of warrenty unless the poster has an extended warranty. Otherwise, I would stick to what the owner manual says. Unfortunately, this would be a no. I don't understand why they tell you to use 5w30, but are forbidden to use 10w30. Does running a little thicker oil when cold, till its hot really going to hurt your vehicle?