On my 2012 I get 16 or so in mixed driving and 17-19 on highway. Tires make a difference I've found. I swapped to some semi-offroad tires and the mileage dropped by at least 1 mpg, maybe more. Changing to Goodrich All-Terrain T/A brought it back up. Strictly highway tires would probably help more. I have a 4WD which might shave a little off the mpg. Wheels are 18 inch.
I've seen people saying that the rear end doesn't make as much of a difference on these newer trucks because of the 6 speed transmissions. I don't know enough about this to agree or disagree with that.
