Best my truck ever got was 22 with the old Predator 65hp program. 65mph-- hand calc'd. It also puked the worst with that program too!!!

 

I lifted this quote from another post, but for what it's worth here it is....

 

OK, I just filled up again this morning, 387.3 miles on 22.165 gal. yields 17.47 MPG. I hand fill to the top of the neck and reset the trip meter every tank full. If you want to squeeze the fuel gage, there's a good article in the December issue of Diesel Power magazine about a guy who is pushing 26+ MPG in a F-350 2X4 with a 7.3 PSD and 6-speed manual tranny.

Among the mods he did are several that most likely won't work for you. He lowered the truck 3" front/4" rear, is running smaller than stock tires on the front(to lower the front end another 2"), put in 3.08 gears(1700rpm@70mph), 203 degree thermostat(claimed 3/4 mpg improvement, more in winter), coolant filter, Evans waterless coolant, disabled turbo backpressure valve(claimed 2+ mpg winter improvement), Excursion front bumper(has longer fairing to control air flow under truck), home made fairing for truck bed(back of cab roof to tailgate, high flow intake, custom burned chip(decreases fueling and advances injection timing below 2000 rpm) and 4" exhaust among others. Like the article says, a Chevy Malibu gets about the same 26 MPG but wouldn't you rather drive a 1-ton truck???

If you want the article but can't find the mag at the news stand, PM me your address and I'll send it to you. Hope this helps...

 

Not a defueled and riced up one

 

I have a 2004 F-350 crewcab SRW LB, 6.0L, 3.73 axle, build Oct 2003, bought new in March 2004, 55,000 miles. Completely stock, making runs to Lafayette, LA on I-10 and Dallas via I-45 from Houston, TX. On cruise control at 65-68 mph I get 20 - 20.5 to and from Lafayette, and 19 - 20 to and from Dallas (I-45 gets a bit hilly north of Houston). Hauling about 300 lbs 10 ft long sheets with tailgate down, no passengers. In city, varies between 15 - 17 mph. No recalls, no problems except once with bad fuel causing water in filter light to come on. A real SOB at night on freeway crawling under left side only to find a special hex wrench needed to drain filter. Finally able to wedge in a flathead screwdriver to remove drain. What a dumb setup. Why couldn't they use the same setup as was on the 7.3L, with that simple filter drain?

I didn't have any trouble with my previous 1999 F-350 Powerstroke, either. Used only a Superchip to gain fuel mileage from about 18 to a little over 20 mpg for over 150,000 miles. Fluids and filters were the only reasons it went to the dealer.

 

IF you don't want to revert back to stock, I would do gears in the truck. You have effectively changed your gear ratio by going to the 35's on your truck lowering your RPM's while increasing your speed if that makes sense..Essentially you 60 mph now and have lower rpm's then before the mod. Being your truck is lifted it also got more drag because of the height. Gears will help get you back to as close to stock ratio's as possible. You want your truck running in the optimum torque/hp range it was designed for. I assume your stock gears are 3.73? If so 4.10 are probably the most you want to go... You will hopefully get back a good portion you lost MPG wise but not all of it due to drag.

P

 

Check into a guy at DP tuners. I put his econo tune on my 05. I am running toyo tires that are equal to 33, 12 X 50. Before the tune I got about 15.5 to 16.8. After his tune the best I got was 20.2 @ 70mph crusing through New Mexico. I also am running a 4" turbo back made by MBRP. Jody from DP won't advance your timing past 1 thousands over top dead center, which is what cause's the most problems with the 6.0 liter. I didn't see much improvment in horse power, but I do like how my truck shifts now. I also just saw an article in diesel power mag about a power elbow from accufab don't know if it works, but it looks like it would in theory, they claim a 1 to 2 mpg increase.