Just saw this thread and had to put in my 2 cents worth. I currently tow with a 2013 Ram 3500 dually mega cab. The rig before was a 2007 Ram 3500 srw. Big difference in stability with the dually.
The day i picked up my Gateway, i talked to a gentleman who delivers rigs from the factory to dealerships, he was driv8ng a new Ford 1 ton diesel, we were talking mileage and he mentiined he was averageing 4mpg while towing and my heart sank since i thought i was going to loose mileage going from a bumper pull to a fw, at that time my '07 was get5ing a little over 10 with the bumper pull trailer and i picked up 2 mpg with the fw.
It had an Edge tuner, cold air intake and 5 inch dpf back exhaust, i got 18-20 empty and averaged 12 towing, the new Ram gets 16 empty and 10-11 towing but it has 4-10 rear end ratio, i just installed an Edge tuner on it and a cold air intake so it should help, i picked up 3 mpg when i did the same work to the '07 so keeping fingers crossed this does the same. The 2013 for some reason it dosn't seem to make much difference in mileage while towing no matter how fast i roll, it stays between 10 and 11 stock, and anywhere from 55-75mph, not towing it makes a big difference. If the tuner does what it is supposed to do, i may end up doing the exhaust on the 13 as well but i don't care for the added noise with the muffler removed.
Took a quick spin after getting everything done and man what a difference so far, way more power and throttle response is amazing, to bad the factory can't get these to run as well stock, potential is obviously there but the epa has thier hands tied.
I don't know how the new 1 ton gassers do, but after towing with a diesel powered rig i don't think i would ever go.back.to gas. And now diesel is lower cost than regular unleaded, which it should have been all along since it is less to produce than gas. We are trying to get away asap so once we do i'll post results with the tuner and intake installed.