Just towed last weekend for the first time with this truck. It's a stone stock 06 F-350 6.0 dually with 4.10 gear. Average mileage on the highway "empty" is around 14.5. Around town is 13-13.5. Last weekend I pulled the enclose race car trailer, approximately 10K lbs, and the truck averaged 9.5 mpg. That's terrible, thought it should've been around 12-12.5. What do you guys think ??

Is there any minor mods that I can do to improve mileage without tearing up the engine or knockin out the head gaskets ?? LMAO What about the 4" exhausts ??? Is'nt there some kind of EGR delete deal that improves mileage ?? I don't need more power, I just want to improve the fuel consumption all the way around.
Any info you guys could put up here on this matter, would be greatly appreciated.

Thanks alot, Frank

Thats bad for a 6.0, my 03 250 got 19 empty and 12 to 13 pulling boats. The earlier 6.0's had more power and got better milage but didn't stay together. I think they detuned them in 04. Remember if it's a dually milage is going to suck. My 08 F450 get under 15 empty on the highway and I've seen under 8 towing a 30' boat. But even with the poor milage its the best truck I've ever hauled boats with.

I've got the exact same truck in an 07.......your numbers mirror mine when towing a 15K go-fast or empty. Since I only drive it 3K a year it isn't worth it to me to do anything about it. I did notice keeping it around 65 on the highway nets much better highway but I can't manage 65.

Sounds about right for the truck. The reason you think it should be better is "most" people just look at the overhead computer not hand calculate. They also do not include ideling etc. Real world fuel economy IMO is hand calculated for the entire tank including all driving. Not just resseting the computer on a down hill and saying "LOOK 25 MPG!" From looking at your boat you have more truck then needed. A single rear wheel 2500 3.73 gears would fit better. EGR DELETE AIR INTAKE AND EXHAUST WILL HELP BUT NOT AS MICH AS YOU WOULD LIKE. Even a performance compter. Snow performance water injection is sweet. Also remember a performance computer will make the factory computer lie even more saying the milage is better then it is.

the rearend kills the mileage. Everything's a compromise.

I agree on the SRW 2500. I have one, but it's gas, not diesel, 2500 HD, and it has the 4.10 rear end, and was told that's the only way it's offered. So, I bought another 06 350 powerstroke like the one I had 4 years ago. That one was the same setup as far as gearing stc. but it got 13-14 on the highway empty, and 11.5 pulling the boat. Now, pulling an enclosed car trailer @ 65 mph, this one gets 9.5. Just thought it would get a lil better than that, kinda like the last one did.
I also pull a 46 Cig, so that's another reason for another diesel dually. The last F-450 got a terrible 7.5 mpg's pulling anything. I towed a friends BMW M-5 from Chicago to Santa Monica Ca. for him a couple years back when the truck was a year old. It averaged 7.5 mpg's for the whole trip, and it was all highway. Got to Ca. and he offered to buy the truck from me, so he bought me a plane ticket back home, and he was the proud owner of a 7.5 mpg 08 F-450. Swore I'd never buy another one again. That one had the 4.88 rear end in it, and that's probally the main reason for the bad mileage tho.
Hav'nt towed the boats yet, so I guess I'll just wait and see how bad it's gonna be. Love the truck, guess I'm just a little disappointed in the poor mileage, that's all. Enough to not even want to drive it that much anymore, unless I have to.

10x
I have a old 96 f250 with the 7.3, 4.10 rear end and when I pull a small box trailer it gets just about as bad as when I pull the boat that weighs 5K more.

With the boat under 70 I get about 10, with the trailer i was only getting 11 -12. I think it is the wind resistance of pulling a big BOX behind you.

this year truck it is hand calc. Speedo and odometer checked and correct.

What is your cruising speed on the highway when empty? Even a dually with 4.10's at normal cruising speeds should be getting better then the 14 range.

I will say a good intake/exhaust/tune will give a nice increase in mileage, any diesel we've owned or friends with just those mods saw pretty large increases in mpg especially on the highway. The 6.0 when done right gives pretty damn good mileage, just have to do "studs" possibly.. you have people who have blown the gasket with the factory tune and you have others with full mods and hardcore tunes with 10's of thousands of miles that aren't "studded" and yet no issues... weird lol.

I have a 2007 dodge 2500 with the 5.9 48000 miles get 20-21 all day long on the highway and 15 - 16 pulling boat and thats on hills and curvy old state highways to the Ozarks 373 gears. Might try 5" exhaust and a programmer might improve the ford but or but you might be limited unless you spend a fortune on upgrades

If it was my truck I would take it to Beans Diesel Performance and tell them to put a 5.9 Cummins and a 3.73 axle in it.