I have kept records since day 1 for 36,000 miles and I have an overall average of 13.9 MPG. I had a low of 8.1 and a high of 20.3. This includes towing a TT weighing 8800 lbs and two fuel tanks full, tow tool boxes and GCW of 16,100 on the CAT scales. Most of my driving has been empty and I drive 70 to 80 at times but normally 70-72. I recently have been setting the cruise at 2000 RPM on the highway where possible. I am totally satisfied with the mileage. Sure beats the 454 4WD 3/4 Suburban I had.