I know we talk about gas mileage a lot with our trucks and we are constantly trying to improve it. I own a 97 F250 with 194k on it and have done a lot of modifications to it. I have tested mileage improvements after each mod. As far as the motor is concerned, I have seen no dramatic gains after each mod (HPX, Stage II Injectors, IC, Beans D60 turbo, Terminator HPOP, intake, exhaust...).

I did have a big change after my installation of the shackle reverse kit which involved swapping in one ton axles (front D60 with matching rear, 4.10 gears) with the one ton suspension. I have heard prior to the gear change (3.56(?) to 4.10) that I should expect a loss in mileage. I also threw on a set of 37" tires and some heavy bumpers and headache rack to go with it, this is the current state which is shown in the pic below. What I did not expect was to get 12 - 14 mpg's after.

I am curious to see if any of you have experience's with improved mpg's or the opposite and what you think is the limiting factor to your changes. Thanks

 

I have a 2wd supercab, 6673, 3 in dp, and stock tunes, 4.10s and i get 15 ish.

the bigger tires and the lift will really kill your mpgs the most.

richard

 

Um, no one here talks about _gas_ mileage....

Did you recalibrate the PSOM for the 37s? If not, you're going faster and farther than the speedometer and odometer indicate, and therefore your actual mileage is higher than what you calculate using the odometer. If it's still calibrated for the stock tires (which are aprx. 31" OD), you're actually getting 2-3 MPG more than what you're calculating.

 

I have not recalibrated it and did not even think about that, good call.

I've wondered if there was an adapter to adapt a 6 speed auto while re-gearing the axles back to 3.56 which would help mpg's on the highway a lot. Has anyone heard of such a thing?

 

My OBS... Regular cab, 2wd, 5 speed, 3.55s... 160/100's, S466 turbo, modded 17* hpop, electric fuel system, DI 7.3 intercooler, tunes are still for 80% nozzles so the pulsewidth is a touch long, and of course the 6637 and exhaust. The gearing of the ZF5 and 3.55s comes pretty close to the final drive of an E4OD with 4.10s. I can get 21mpg in my street race tune on longer trips cruising at 65mph (2000 rpm). I normally get about 18.5 mpg going to and from work which usually includes at least one full throttle blast up to 100ish mph in the race tune.

My SD... Extended cab, 4x4, ZF6, 3.73 gears.. 6637, 4" exhaust, stock AD split shots, stock tuning, stock everything. 15.8mpg is the best I've gotten so far.

 

My tunes haven't been updated since the new turbo, would re-tuning that help?

 

It goes way beyond an adapter. The PCM has to know how to shift any automatic transmission. Our PCMs can only shift an E4OD. For anything exotic like a 6-speed, you'd need a stand-alone transmission controller.

 

Doubt it.

10char

 

Best mpg Ive gotten is 19, worse is about 10 driving like a bat out of hell.

I got 4.10 gears so anything over 65mph my mpg goes into the trash.

 

ANother point is that I do have the ZF5 as well so gearing for me is that much lower. Might be a good idea to consider an auto swap

 

Miine went downhill towing when I went to 4.10's. I was able to stay in the throttle more, had more control over the egt's at higher rpm's. It went down even more with the new turbo, same reason. It will probably go down even more after I get done with the dually conversion. I used to be able to get upwards of 20 with 3.55's in more of stock form, empty. Now, I really don't know for sure, I just don't drive it empty hardly at all, but it wouldn't get that good. That's ok though, I didn't build mine to worry about mileage.

 

The gears are the big issue. I also consider going back to 3.55's but with the manual tranny I feel like it would be difficult to get going when loaded esp on 37's

 

Stock form keeping rpms at 1850 I've seen 23mpg
W/ 4.10s 35's. Using google maps to calculate miles, then divide by how many gallons I pump.

Modded form constant 16 no matter what.

 

6637, 3" DP,open exhaust, all stock, I have been getting 16-17 if I drive below 65. I usually do. When I keep it at 70, it goes to about 14. I just did an oil change over to Rotella 10w30 from 15w40. I seem to be going a little farther on this tank, so we'll see if that netted any difference. I am not going for mileage as much as I am longevity.

 

I've seen 18 once in my truck. Typically about 15-16 mixed.