So now I've travelled from Mesa, AZ to Santa Fe, NM. I'm impressed by that Duramax. The trailer is 12000# dry. Its go tons of power in the mountains. The exhaust brake works awesome in the passes. I am sort of a ford guy I guess but this truck really rocks. Its a little light when the interstate is rough(I don't like when the trailer tends to pull the trailer upwards on some unexpected bumps) but it still feels planted with strong cross winds. Cruising speed has been 63-71mph. It runs real nice at 66mph, I wonder if that's because we are on the old route 66???