Bought my 2012 Ram 2500 w/ Cummins Highoutput Dec. 2012 to pull our 5th wheel trailer. Trailer is 37 ft. with pin weight of 2480 lbs. 12-15-12:When we made our first run to Arizona we got 10-12 MPG. Comming into Verde Valley on the 6% down hill grade was amazing... The towhaul mod and exhaust brake made the trip enjoyable.
2-23-13: Just returned from Julian in the S. Calif mountains and the MPG has now dropped to 9-10 MPG and we now have 4000 miles on the truck.
I'm changing the oil this week and the fuel water seperater. I'm also going to try some cetane boost from Walmart to see if that will help the MPG. The (Beast) truck runs better on the AZ fuel than the Calif. fuels.