I'd buy it, 256,000 on a Cummins clock is nothing! I'm driving one in a Ottawa shag truck (Yes same engine!) that has 891,000+ on the clock, and the only thing that had been done to it is a set of injectors & a pump. I guarantee it has seen more abuse than you can do to one. I probably pull 20 to thirty trailers a day, weighing in excess of 56,000lbs. This thing uses hardly any oil. So ya better buy it!