a cummins motor is the best their is .
a 5.9 Cummins is the best there is. If I'm not mistaken all the '09s are a 6.7 and your not gonna enjoy the fuel mileage if its stock there's a lot of emissions b.s. on em. I believe Justincorbell has a pretty nice 6.7 that he's done quite a bit to maybe he'll chime in