We have 56,600 miles on our Freightliner M2 and will never have to buy another Truck to pull our 5th wheel. I haven't checked the mileage but it gets as good or more than any of the GM 3500HDs we have owned when we are towing. I filled the tanks last Sept. (160 gals) and still have 1/4 of a tank and since we got to Gulf Shores in Oct I have driven the Truck about 25 miles per week. We double tow the Chevy HHR and drive it while we are here. I very seldom fill the tanks unless the price is down, doesn't look like its going down much more so I will just put on 50 gals and wait to see if it goes down this spring. It does seem like the Mercedes Diesel does get good mileage, considering what its towing, but it only has 300 hp but has a 1,000 lbs or Torq. Very few HDT/MDT owners check fuel mileage, fuel mileage isn't something you think about will running a Big Truck that in our case the weight of the Truck is 14,060 lbs. GBY....