2006 Dodge 2500 4x4 Mega Cab 3.73 no muffler CAT still on it. 15.6 MPG AVG 13.8 pulling a 18 foot car trailer with an XP1K four seater. Hand calculated as I found the gauge to be about 2 MPG long.
I live 20 miles outside of any town so it's mostly highway, however I stomp on it to get up to speed.
I tried real hard to drive like an old man for a full tank and got 17.6 AVG.