There has got to be some seriously "creative math" being used in this thread. My truck runs like new and never even gets into the high teens.

 

I've had at least 4 firstgens that I've tracked mileage on, I think my worst tank ever is 15. I had a 91.5 D250 5 speed(stock) that got 18-23, it even got 18 towing my ski boat. When I track mileage I go to the same pump, fill to the pump stops on its own, and I always make sure the speedo is accurate. And yes, I know how to do math.

 

I dont know about creative math, but I have gotten 23.5 and 23.8 running the same stretch of road, same distance, trying my hardest to drive with an egg under the peddle and not over 60 mph, ( i wasn't in a hurry). Oh this was with the 99. I know for a fact that Dad's 93 2wd will beat me, and the father in laws 92 with a topper thats about 4 feet over the cab ( farmer's market special) and 3.07s with getrag can regularly do in the high teens on the interstate, and that things like driving a brick wall at 70 mph. So i don't think its out of the realm of possibility. Its all in how you drive it, i guess.

 

Also, trucks w/ BHAF's, adjusted pumps, exhausts etc will get better mileage.

 

I dont think the high 20s is unobtainable. 30- I'd have to see to believe, then do some creative paperwork to make it legally mine

Just because your pickup has never seen 20 doesnt mean someone else's wont. How do you knwo yours wouldnt do better with some air and fuel enhancements? what about your timing, valve adjustments, injector spray pattern, etc? There are at least a dozen variables that influence fuel economy (or the lack thereof in some cases- If I cant get 20+ hwy, I start checking things), and everything has to fall into place to get it.

The last dually I had was mechanically identical to the one the P.O.'s dad had, but his dad's always got about 3mpg better. Same truck, gearing, transmission, etc. It's just in how they are assembled, broke in, and driven from the get-go.

DP