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 recent trips to Cal and then again to Colorado and New Mexico, we averaged 12.1 with our 2006, 131K miles of a D/A, 3.73 rear end and about 10,000#'s of fifth wheel. Flat country and steep grades. I keep my speed at 60.