Link to video Even with 3.92 gears is got great mpg - 33+ mpg at 65 mph :E. Also of note was the EVIC mpg was low compared to actual, just like the other Ram trucks they tested.
I am not sure how you can call that anything but impressive. RAM hit the mark for their target market - people who put MPG high on their priority list.
I'd be willing to bet that the 5.0 Cummins will be at least 20% lower in MPG.