My observations bear out what I read in the forums before I bought the truck. Unloaded around town it's usually about 14. I can baby it and do better, up to 17, but not with normal driving. Regens are the reason- every time the mileage creeps up the regen kicks in and blows more fuel out the exhaust.
OTOH, when towing, this is the most fuel efficient one I've had, much to my surprise. Just did a coast to coast trip with a bike in the bed and travel trailer on the rear. Westbound 9. 5 mpg, which considering the tires, lift, load, constant headwinds, and 75 mph speed was reasonable.
Eastbound 11. 3 mpg dialing it back to 65-70 and less wind. I've done this route a bunch of times with other trucks and this one's as fuel efficient with a load on as the best of them were.
I know a lot of people can do better on mileage, but I drive to minimize transit time, not mpg. These numbers towing are the best I've ever done under similar conditions.
PS- it's a SRW, so no diff than a 2500 so far as mpg...