just finished a 2588 mile trip pulling about 12000 lbs. (5th wheel)DW kept track and here is the low 9.4 and high 11.9-2013 Dodge 3500 4x4 with 6 speed stick-truck did a very good job-I was impressed!...
On roughly a 5000 mile trip from Nebraska to the west coast and back I got 11.73 mpg hand calculated in my 2011 Duramax 3500 SRW pulling my 12k Cardinal 5th wheel. I was driving right around 60 mph the entire trip when on the highway. This was all kinds of different terrain as you might imagine. I was pleased with the results.