xj_punk said:10% to be exact, i used the gps on it.
but still, i thought i would be getting better mileage than that
that is still extremely low on a cummins...even in my Powerstroke I have never gotten lower than mid 14s while towing. Herzog's Cummins, I believe, was doing the same thing and he did something and it fixed it...let me find where he posted about it...