I run a 6V92TA DDEC IV with a V731 ATEC with O/D transmission. At 65 mph I average 7 to 8 mpg on an imperial gallon. Total weight with a 5000 lb truck in tow is 37000 lbs. I know it is a 2 stroke engine which isn't the most fuel efficient engine but not many are more reliable. I question some of the fuel mileage figures above. Some of the newer small motorhomes don't give the mpg's stated.