getting ready to buy used
dodge Diesel. Which is better on fuel towing and non-towing??

 

The 6.7s non deleted will get crappy mpgs period. The later 5.9's became the same way( I think in 05 or 06 cant remember). My 02 5.9 I can get 22mpg on the highway. In town it all depends around 15-18mpg. Last time I towed I had 11-12k behind me and I was around 11mpg. Got to remember this is with a 6 speed. Autos arent gonna get as good mpgs

 

My 2004.5 doesn't get as good mileage as my 2001 did empty but it gets slightly better mileage pulling our 9k toy hauler with much more power. Mostly my truck only comes out to tow so that's what I'm most concerned with.

 

My 08 6.7 auto with 3.73 gears, 32" tires, 4wd got 11-12 mpg average over 4800 miles while towing about a 14k pound trailer.

If you're hauling a heavy load, the 6.7/68rfe combo is EONS better than the 5.9 auto. The exhaust brake function is awesome, the gearing is awesome, it's just a much smoother setup. I towed that trailer going back across the same trip (more or less) with my 98 12-valve and 47re and got the same fuel economy, but I really had to watch my trans temp in stop and go/town traffic, and it was working a lot harder with the wider gear ratios while getting up to speed. Once cruising, it was pie either way.