I had a 04 Quad cab 4x4 shortbed that would get 17 mpg around town and up to 21 mpg on the hwy.

I fell a sleep in the 04 and totaled it in 2010. I bought a 2500 crewcab gasser 4x4 and kept it 2 years and sold it because it got like 13 MPG at best and much less if I towed anything

So I looked and found a low mile 06 Quad cab long bed 4x4 (60 K on the clock in 2012) it now has 91K on the clock. (I drive a company car now used to drive my 04 dodge for work) I wanted an 06 because it was the last of the 5.9s and no emissions

I get 13-15 mpg in the 06 truck always.. In town..Hwy... I just pulled an empty 20' gooseneck back from TX and got 14.5 MPG at 70 mpg. Both trucks had 3.73 rear diffs.

Why the mileage difference ?? the 04 was stock except for hummer wheels and 31.5. The 06 has big exhaust an Air-raid filter and 285 tires?????

Long bed VS short makes that much difference??

 

Are the odometers reading correctly on both? (Calibrated to tire size?)

Anyway, I had an 03 quad 4x4 HO SRW 3500 nv5600 and 3.73's. It could get 21 on the highway if you kept the speed down. 15-16 if it was all short trips in town. Everything stock.

Now have a 3500 dual, quad 4x4, 3.73 G56, 3.73. 19 is about the highest it will get I the highway, and similar 15mpg if all in town.

Part of that is the duals, but I'm sure part of it is the extra injection event, cat, and extra power of the 600 engine.

When the 04.5 came out there were theads about not getting the mpg that the 03-04 got.

Still, your new truck should get better highway than what you are seeing,
Assuming speeds are reasonable.

 

the 06 has a very complex in-cylinder egr system to meet the latest level of emissions, we run a fleet of 06's and in 06 we spent a lot of money trying to remove it, i went to a seminar put on by cummins and one of the engineers that worked on the design was there and gave a lecture on how they did it, and he was very proud to answer all of my questions, he was amazed that i took so much interest in the smog reduction system, what we had to do in 06 to help got easier and less expensive over the years, it is to expensive to remove it all but you can get rid of most of it, you will get your 21 mpg back and reduce the carbon in your oil by 75%, the first thing is to get efi live by anarchy, this alone will gain 3 mpg, we have our own shop and do all of our mechanic work ourselves, so you be the judge of where you want to stop, the next thing is to reduce drive pressure on the turbo, all of the big rigs use 5" exhaust so parts are cheaper, we start out using a farm boys straight pipe kit, we get our big rig parts from ryder truck parts so the number on the resonator and muffler are donaldson, resonator M090072, muffler M101181, you will need about four more 5"clamps, it takes me about three hours by myself to change it out, for your first time allow six hours with a helper at times, getting the old one off is more time consuming than you would think, the tools needed are sae 7/16 for the turbo clamp either 9/16 or 5/8 for the clamps, next is to mod the turbo, total cost about $5 but to lengthy to explain here, if you get this far pm me and i will send pix and how to, next item will gain you about one to one and a half mpg, you figure the payback period and see if you want to do it, change out the camshaft, in 06 PDR in canada had the best timing and duration for what we wanted, the cams cost us $500, others have told us colt has a low rpm high torque fuel economy cam that is even better than our PDR