6.0 MPG, Help me before I trash it

Hey everyone. I'm a newbie to Diesel trucks, but when I needed a truck to make our pulls cross country everyone said this was the way to go. Well after many of trips and different configurations I'm just at a loss here. The truck is a 06 f250 td super crew. The previous owner has some larger tires, but nothin crazy on it (305/70/17). I had ford reflash the computer, they redid my headgasket before I started towing. With the ford reflash, i was doing under 8mpg with a 7500lb tow @70-75mph. I decided to get superchips tuner and running different setups, the best was the performance which is getting me 9.7mpg. I've told ford about it and they can't figure it out or even care since there isn't a standard for these trucks. My best mpg was almost 14 mpg with no towing on the highway at 65mph. What is going on here, I could have been doing the same with a gas V8. Oh, also I got the truck with 30,000 miles. It has 44,000 on it now. Any help or suggestions are much appreciated. The only reason I haven't done any exhaust or intake is because I believe the factory package should be getting better before I dump money into something I'm gonna have to trade.  

you didnt specify if you have a manual or automatic trans. ultimately, if you keep your rpm's down, you will get better mileage. i have an 02 ford with a 7.3. if i keep it under 2,000rpm's i.e.- at 68mph im pulling 1900rpm's with an automatic and 35" tires and i get around 18mpg empty. if i go over 2,000rpm's (70-75mph) it will drop to 12-13mph. free up the exaust and intake, thats gonna make a difference. the stock stuff is garbage.if you have to pull your trailer at 70-75mph and you have a manual trans, you might consider an overdrive unit of some sort a gear vendor or mitchell or something like that to help bring down your rpms.or you could trash it and buy an older 7.3L. i can get 12-14mpg towing 7500lbs. good luck  
its like wipeing your ass with a hula hoop, its endless

Sorry, yeah it is a automatic. For the most part the truck is revin at 2k to 2200 at most. My dilema is even drafting a semi the whole way home one night. I did a full tank behind the semi, at about 1900 rpm and I only achieved 12mpg. I'd really hate to add money to this truck and then be in the same place when it comes to mpg's. I hear people on the boards making in the 16-18 range on the highway pulling. Someone local did ask me what rear end gear ratio I had. He said this makes a huge difference. How can I find this out? Will my vin# have this info at ford?

Thanks for any help and suggestions  

look in the door jam, it will say axle on that sticker, what code is it

IF it is a C1 then it is a 3.73 limited slip  
Let the good coal roll
I thought I was wrong once but I was mistaken!!!

if your running over 2000 its probably a 4:10. mine is a 4:10 and i normally run around 2100 at 75 mph. i dont do much towing so i get around 16 or 17 mpg. look into electric fans. they add a lot more mileage. if your driving on the highway a lot, the fans will probably never run, the ram air should be enought to keep it cool.  
1996 Ram 2500 reg. cab longbox, #6 plate, 191 Deliver valves, 60 hp injectors, star wheel turned up a lot, AFE Stage 2 intake into a Phat Shaft 62 wastgate set at 40 psi, 4" straight pipe, Auto Meter Gauges, ATS tranny and TC (unfortunately), Dick Cepek FC-II A/T 265 LR16 (good tires). FS-2500 Bypass Filter. The only hands that work on my truck are my own.

Member - Blowin' Smoke Gang

Ok so your normally hauling 7,500Ib at about 70-75mph. You have to take into account that when your traveling at that kind of speed with that weight you're going to get crappy mileage diesel or gas. But you shouldn't be getting the crappy mileage that you're getting, so I recommend getting an aftermarket exhaust and cold air intake, a fuel additive would help as well. Have you had problems with your injectors? The 6.0 has had quite a few problems, so if you do decide to drop the truck I would look into finding a nice 2002 7.3 with the same options as your truck. You could also look at the Dodge and even though it's a Dodge, it has a Cummins engine under the hood. Just do the necessary upgrades and go the speed limit when you're hauling!  
1997 F-350 regular cab, SRW, aFe stage two cold air intake.

I don't think it would be wise to drop a lot of money in this thing, like said before towing that much at that speed you are not going to get 20 but you should be getting better then 8, you drop $100's in this thing for intake, exhaust, etc. and you might get what a stock 6.0 should, there has to be something wrong I would look into the injectors, that was a big issue for the 6.0 or look into a Dodge like stated before, i'm lovin mine even though it's a Dodge      
06 Dodge Cummins 2500 4x4, Edge Juice w/ Attitude w/ Hot Unlock, Predator 2018 STG 3, S@B Air Intake, CFM+ Intake Manifold, 5" Turboback Magnaflow, South Bend DD 3600 Street Comp, Top Gun Custumz leveling kit. Dyno- 495HP-962TQ, 15.20 in the 1/4 Hot only

are you doing the fuel miles yourself or letting the conputer do this cause mine says one thing and do yourself its alot differnt. But thats really bad I hate to say it I guy I went to school with has factory gears and 38 on his cant use it to tow anymore but he gets better than you in his 6.0  
2001 dodge with 5in exhaust k@n intake with edge comp box,2in leveling, added holley blue lift pump kit member-"Blowing Smoke Gang" Ranchhand bumbers

well i got everything you can imagine on my 02 f250 i started with 12 mtg and i ended up with 12 mtg and i dont hardly pull anything and its the same if i drive slow or fast never changes  
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i have an 02 with a 7.3 and i get 14 mpg no matter what towing, driving normal or playing with edge juice with attitude  

Im a cummins mechanic but have worked on a lot of powerstrokes,they dont get good fuel milleage but if youre running around2000rpm you should be geting better milleage and you can rule out youre gear ratio (diff). Check youre charged air side of the turbo and make sure you dont have a loose clamp or pin hole, trust me a small leak makes a big differance.  
A real toy for big boys.I installed a 5.9-B Cummins, P-7100 inline stage one pump,  banks cooler,5in exh,removable air bags for towing, 1in body lift,2in hanger lift,2 12in elect fans, customized mounting,(eng mounts,intake piping,trans adapter etc) Runs on home made bio-fuel at 70 cents a Gal.

i wouldnt drop anymore money into it because ever since ford left the 7.3 they have had problems so i would trade it off get a 7.3 or a dodge because when i pull with mine i get around 15 and thats with a 38 foot gooseneck and a johndeere on it but highway i can believe it but im gettin 21-22 going 65 and 19-20 at 75 but my dad has a 7.3 he has a edge evolution stacked with edge juice with attitude and exhaust and intake he gets around 20 going 75 im not sure about towing because he always calls me if he needs something hauled somewhere  

i got an 01 dodge by the way 5in exhaust, aem intake,cfm intake manifold, edge comp  

I also have a 6.0, but get a consistent 18.5-20 MPG in a 6-speed F250 4X4, usually at 65-75 MPH. I agree with you; your mileage should be better. I suspect two items: 1.) The dealer reflashed your motor, likely causing a loss of efficiency; 2.) Check your injectors; they might be leaking. If the oil level increases with use, you obviously have this problem as well. In my case, the dealer reflashed my truck AGAINST MY WILL AND DIRECT INSTRUCTION!!! (nearly got into a fistfight over this one!)I then overrode their reflash with a Bullydog chip. I have not been back to any dealership since then; I strongly suspect that there must have been an order from Ford Corporate to do this; as nobody could tell me what the new programming REALLY did, and my EGTs seemed lower, as did my mileage. To you other 6.0 owners: Trust Nobody.

The good news: My 6.0 has been very reliable at 60,000 miles. But also note that I do not tow much, use synthetic Mobil 1 religiously, and always let my motor warm up before I ask for any power out of it. It also has the Bullydog intake and 4" exhast.

If I were you, I'd check everything I could think of, and avoid the Ford dealerships like you had my experience: nearly getting assaulted by Ford personnel when trying to prevent the sabotage of a vehicle I paid for. Enough said.  

Some other info and ideas that might help: My rig turns 2000 RPM at 70mph, runs ~3 psi boost and an EGT of ~525 at this speed. It is an extended cab with a manual; 4X4 (unengaged the vast majority of the time). The pickup bed is open; no cover (yet). Stock ride height. No propane, either. These figures are near sea level in SoCal, on a 55 degree day. The EGTs were higher at 6000 ft in New Mexico.

The suggestion to look at the intercooler tubes for leaks is a good one, and evidence of leaks might not be as obvious as one would hope: mine were spotless on top, but filthy (grease and sand) below, showing perhaps that somebody had washed them before I actually got the truck. Check your air filter, too.

Good luck!