My first DP was a Coachmen with a 5.9L Cummins and I got an honest 10 mpg. However, I now drive an American Coach with a 8.3L Cummins and according to my computer I average about 8. A lot depends on how you drive and the tow vehicle doesn't seem to affect the mileage. My current coach has a "sweet spot" around 65-66 mph where it seems to get the best mileage. Your results may vary. However, the comfort and ride quality will more than make up for the cost of driving it. Have fun!