I have a 07 dodge 2500 with the 6.7 cummins and it gets 14 mpg in the city and 20 on the interstate. The 5.9 cummins got 25 to 28 just about anywhere you went. I wish mine would have been the 5.9. I have had both and there isn't that much difference in pulling unless your really into to it. I will say that the engine brake is nice when pulling my 25 ft. gooseneck full of oak.