Answer to: ISX vs DD15 vs C15I had an '05 ISX. For what it's worth, I have never driven anything except Cummins in my 21 years of driving so naturally, when I bought my first truck I opted for the ISX. EGR after 180k. At 595k a wristpin circlip dislodged and destroyed the block. Reconditioned block and brand new head for $25000 and 400k miles later I broke the crankshaft in two. I don't beat my truck. Never have, never will. But I will never own another Cumapart.