I am pulling a 34RL Cedar Creek with a 2008 Ram, 3/4ton, 6.7L Cummins, 68RFE auto, Mega Cab, 4X4. On my last trip out west this year, I average around 11 MPG pulling at 60 MPH with my lowest mileage being 8.3 MPG into a 20 MPH to 40 MPH headwind one day. When I am not towing the camper I have seen a high of 20 MPG to a low of 17 MPG at 65 to 70 MPH. These are all hand calculated fuel mileage numbers and not from the LIE-O-Meter.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67