I just drove from Clovis, CA to Quartzsite, AZ and was getting from 18.5 towing/city, to 25.5 towing on a flat part of I10. Last tank is showing 19.9, all towing.
With the 8 speed trans, you have a huge range of gears and with 420 foot lbs of torque at 2000 RPM, she pulls like a train. Pulling a 5.0 TA would be a dream.
I'm very happy with my 2014 Ram Ecodiesel 4X4.