But the owners manual and top of oil cap says.........2015 GMC Sierra, 5.3L Ecotech
5w30 Valvoline Restore & Protect (yeah I know, I'm supposed to use 0w20, don't shoot me)
CarQuest Premium filter
Then the thin crowd will say for potentially better MPG you could try 0W-16
0w-20, 5w-20, 5w-30, 0w-40 if you have it, rock it. Use up and rotate stash if possible.