1999 f350 cc 2wd 7.3auto with Garrett gt40 turbo, 200/100 injectors, 4"down pipe into 5"exhaust, adrenaline hpop, custom camshaft, head work, bigger inter cooler, 6 position chip tuned by tony wildman, full built trans, 3:73 rears basically stock size tires 16s lowered 3/5.. City 14-15 empty (would be a lil better but drive it like I stole it everywhere) highway 18-19 at 75 mph empty. Towing 16k highway 12-14 avg at 70-72mph.

2012 F450 4.30 gears about 14 mpg empty at 70-72 mph, I tow 23,000 goose neck dual tire tandem and mileage is below 8 mpg, I don't even watch when towing just watch fuel gauge as to when I need to refuel. No chips, mods, bone stock.

Not a dually, 2500HD Duramax, DPF/cat delete, EGR blockoff, 8000lb tow tune with EFI live, just did a quick trip to Jax Fl towing a 32ft enclosed trailer, some fuel runs were right at 10, then some a tad over 12, all hand cal. seemed brand of fuel affected mileage..anybody else notice that ? this was running 70-75 with 3:73 and 285 tires...

Yes up here winter blend fuels suck.

2013 Chev 3500 Duelly, Diesel. Empty, 16.8-17.2 (dash) driving in the 73 mph range. Loaded, makes a difference on size and type of boat, but generally I am in the 9.8-10.3 range. Most of the boats I have hauled with it are Top Guns and Outerlimits. The OL's generally get better mileage, take it for what it is worth, but the last few I have hauled I got 11.2. Now, Center Councils..... Pull like a anchor... 8.1.

I had a 09 Chev 3500 Duelly before this one, was consistently about 2 mpg less in every category.

I had a 99 crew cab chevy with same setup....had a hypertech tune in mine and all it could do was 10/11 city/hwy and 7-8 towing a 30' scarab......then i installed a 6" lift with 35's and had to drive with a tanker hooked to the truck to keep up with the gas demand!!

I will say this though....from reading the forums about these trucks/motors (454 vortec)......best thing you can do to them is a custom tune by someone who knows what they are doing...like Nelson or Westers etc.....and also they need bigger injectors then what they have stock

2011 ford f350 with 6.7 diesel,3.73 gears truck is totally stock,18 mpg at 70 mph empty,10.x towing the fountain.the engine is so quiet compared to my old 05 f250 .

2010 F350 4x4 Crew LWB 6.4 all stock.

No towing data but 14-15 from S Fla to Destin to LOTO and back running 75ish most of the way.

That,s a miracle right there , hand calc or lie-o-meter .

Cash, delete all the emissions crap & get some good custom tunes. Makes the 6.4 a completely different truck.