DodgeVoltage wrote:
It's not exactly the comparison you are asking, but might give you an idea- my 2010 Ram 3500 dually, 4x4, megacab gets the same mileage as my 2009 GMC 2500 SRW, crew cab, Duramax, 4x4. Both consistanly get 14.5 mpg. Occasionally, my Ram will do better by a mpg, but usually pretty close. Those numbers are empty, not towing.
I think there must be something wrong with your Chevy. I Don't think I could get either my 03 or 2010 Duramaxs to burn that much fuel non towing nor have I heard of another Duramax incapable of at least 18 mpg running empty.