After having a '97 2500 2x4 and getting 21 hiway 17 city and 12 pulling a 35 ft FW I'm disappointed in my new to me '13 3500 CC, DRW, 4x4, auto, 3.42 diffs that gets 16/17 mixed city/hiway and 8/9 towing a heavier 35 ft FW. I still love the truck, diesels should be inline 6's.