I have an 07 QC 4 wh drive with the 6.7 and when NOT towing I get (hand calculated) 13 MPG in the city and 18 MPG on the highway. When towing my 28 Ft trailer loaded with the race car, fuel, tools and generator I get right at 11 MPG so he should get way better then me with that earlier diesel as mine has that stupid DPF system and is all stock.