My Cummins was a 2002 with HO and 6 speed manual. I averaged 17 in mixed mostly city driving. Pulling an 8,000# trailer on the highway it would do 13. I had the gauges (EGT and boost) and 4" stainless exhaust. PO had installed different injectors, a South Bend clutch and I had a timing kit that I never felt the need to install. If you can afford the maintenance, go for it, every man needs to own a locomotive once in his life I loved it. Would I own another? Only if I needed the power every day and would use it like they should be used