I am a dodge guy....well that's not true....i am a cummins guy.....the duramax is a phenomenal engine and Chevy makes prolly the most comfortable, best driving truck on the market.....however....they suck ass to work on and parts are $$$. The cummins motors are just the opposite.....they are simple to work on, every thing is easily accessible and parts are reasonably cheap.
Everything eventually needs repairs...so this is just some food for thought. My truck average 16-17 during daily driving and 12-15 towing my trail rig.
09 Dodge 2500 w/ a Cummins, dd/towrig
85 Toyota Pickup, 1tons, coilovers, 40's, ect