Being that yours is a 2011, it's not a fair comparison. But I've got a 2004 Crew Cab 1500 with the 5.3L V8, and mine is 2WD. City driving - 15-16 mpg, Highway driving @ 75mph - 17 mpg, Highway driving at 65 mph - 18 mpg.
That is about what I get on the same truck. It sits in the shop hooked to my boat and I drive a Hyundai for running around. It gets 35mpg. The truck is a '03 with less than 50k miles.