If a truck has had regular maintnance,and has not been hammered into the ground,..........How many miles could you expect to get out of a series 50 detroit diesel before needing a major overhual ? THE 50 SERIES IS A 4 CYL. VERSION OF THE 60 SERIES. Please keep personal comment to yourself,and only answer if you actually know something about commercial diesel engines,.....in other words....ADULTS ONLY PLEASE! Thanks For The Help, Rob in PA.