I would like to hear what kind of fuel mileage you are getting when towing a load (and the size\weight of the load). I have a Early 2007 (LBZ) crew cab 3500 Dually with the 6 Allison 4wd 3.73 rear that is about 7000 miles old and I feel my fuel mileage is way too low. I am in the trailer business and I travel a lot pulling heavy goosenecks. On recent long highway trips, running empty at around 70-75 I would get about 13.5-14 MPG. When I hook up to a small trailer (18ft dual axle lowboy empty 2000lbs) It will drop to 11MPG. When I hook up to a larger trailer (25'-30' Dual tandem dovetail Gooseneck 5500lbs empty) It will drop down to 8-9MPG. If I put my tractor up on the trailer (Older International 656 about 6000lbs + 5500lbs of Trailer = 11500 Total) It can drop in the range of 7-8MPG. My alltime worst was yesterday, (44' gooseneck with a 40' gooseneck on top of that for around 15-18,000lbs total) will drop my mileage as low as 6.5MPG in some hills and 8MPG on smooth ground. All of these figures are for EMPTY trailer (except the tractor example). I expected better than this when I spent 45K on a truck. Is this normal???