To the op just fwiw the new yukon and tahoes are nice but they have some issues that are lacking the 0w-20 is fairly expensive 8 quarts vs the 5w30 6 quarts change she's used to with the older model, the afm is a little better but the same question gets asked at work all the time how do I get better milage and the same answer is always given it depends on your foot and input. I never mention the fact that they are not aerodynamic sleek missiles that cut air they are rolling tanks in a nut shell that way it does not offened the fact they spent 80-90,000 on a vehicle that me personally is way over priced. demand has driven that price there and as more technology is added the price will continue to increase also to aid you in headaches stay away from 22in wheels they are nightmares for customer and techs alike yes they look good but after you change 4 sets of tires on one vehicle cause road force is out on the same vehicle you eventually want to change them. There are other issues that I can't post as they are not my information to give out but thats just part of it you know