My 1992 Dodge Cummins gets 21-22 mpg in town 26+mpg highway and 17 mpg towing flat land 13-14 mpg mountain.my 1982 Suburban diesel (on the rare occasions when it actually ran) got 14-16 mpg in town 18 highway and 10 mpg towing flat land forget about mountain. 6 cylinders standing are much better than 8 cylinders reclining. Jim Smith