My truck has a 6.7 liter Diesel, which is very thirsty. I get 11.5 - 13 mpg, even with the tailgate down. I hate to say it, but my '06 Hummer H2 does better than this! I did have a '99 Dodge 5.9 Cummins which averaged 18 mpg on each tank, long trips 21 - 24 mpg were normal. Besides economy, this thing has immense power, I have 35 inch tires on it and the torque abounds. I hope this tranny can handle the power better than the '99s. I will definitely upgrade to leather seats, the copilot complains there is no heat and limited adjustments on the right side. All the storage compartments are great & make good use of unused voids. Style beats Chevy & Ford. No problems with vibrations.
Must mention: I only have 1500 miles on it so far, so still a new truck. Exterior style, red is hot! 6.7 liter Cummins is potent and quiet(unlike my old '99). Much better use of space in cab. Dash is tidy, like the hidden cup holder tray.
What were the engineers thinking with the fuel prices of today? I am agressively searching aftermarket vendors for economy boosting add-ons. Why not offer leather in SLT? Or put a class 4 hitch under the bumper, standard? Need more handles to help you into the 4x4. Wimpy front bumper.