Well I just completed a 1100 mile trip Towing my 8k pound Travel Trailer towing with my HdZR2 .Truck done great no issues plenty of power seemed to use a little less DEF than my 21 did on similar trips . Overall Fuel milage was about 9.5-10 running about 70 . The last 3-400 miles we had a 20 mph head wind our mileage dropped to 7.1 MPG I burned 30 gallons of Diesel in 218 miles . The diesel is great power wise but towing it likes the Fuel . Without towing highway I am averaging around 18-19 Mpg . What are you guys seeing for mileage ? You always hear people claim ridiculous MPG numbers towing that I have never been able to achieve .