Another poach of my own post with some gas mileage info:
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Did our yearly April UT trip but first time with this rig.
Pickup info: 2024 Ford F250 Supercab with 7.3L gas and 3.73 rear diff. Max payload on my truck is 3,195 and GVWR is 10,400.
With Supertramp, my wife and I in the cab, all gear (food, water, clothes, chairs, tools, recovery gear, air compressor, etc.), the CAT Scale said we had 2,315lb of payload and 9,520lb gross weight (4,540F / 4,980R). That is 880 below max. So nice to be that far BELOW max with a heavy duty pickup rather than that far OVER max like on a Fullsize pickup.
Pickup has around 4,000 miles on it so engine may continue to loosen up a bit and slightly improve with more miles.
Odometer reading was 1,413. Tires are changed from stock 275/65R20 to 285/75R18 so 2.1% larger diameter. Corrected mileage is 1,443 miles. This was 540 miles of highway and interstate. 50 miles of that was slower canyon roads, but mostly 75mph and 80+mph as we ran the speed limit + the entire trip. Had strong headwinds for several hours, too. Then four days of gravel roads or slow, rough trails with a few minor sections of highway to connect trails. Then the same 540 miles home of high speed highway and interstate.
108.43 gallons of fuel used per the pump readout. Pickup gauge calculated 11.3mpg. Hand calculated is 13.03mpg based on uncorrected odometer reading of 1,413 miles and calculates to 13.31mpg using 2.1% corrected mile number of 1,443.
Very happy with 13.3mpg. My Tundra with 4.6L V8 with OEV CAMP-X and similar weight, would get the same mileage or 1mpg less gas mileage than the Superduty in same conditions (high speed highway, gravel roads, trail driving, etc.). In the six speed Tundra, I would mostly lock out 5th and 6th and run about 3,000 - 3,200rpm in 4th. The 7.3L, 10 speed w/3.73 rear diff lopes along in 10th gear except when it gets hilly where it would shift as low as 8th (still an overdrive) or sometimes 7th. When it downshifts, it holds the gear rather than trying to prematurely upshift again like the Tundra. So less manual locking out taller gears with the F250 when driving hilly interstates and highways. I didn't record cruising rpm at different speeds, but seems it mostly hung around 1,100 - 1,200 rpm. On gravel roads going 40mph to 60mph, would easily pull 8th, 9th or even 10th gear, though I often locked out 10th and sometimes 9th depending on how long the straightaways were . On the slower sections (30mph - 40mph) or with lots of curves and turns, I'd lock out all three overdrives and limit the transmission to 1:1 (7th gear) to reduce shifting., but was amazed how the grunt of the 7.3 would allow upshifts and holding a gear at such low speeds. Much different personality, as expected, than the 4.6L V8 that liked to rev to make power/torque.
For the trail driving, 4hi was appropriate most of the time. 1st is really quite low and I only shifted the transfer case to 4lo a few times for particular hills or obstacles and also for a few other sections just to play with it. Stock FX4 had plenty of clearance even in some ledges and interesting terrain. Nothing crazy on this trip, though, and limited to trails rated 4/10. I used to run 4lo a lot more in the Tundra and liked manually shifting while in 4lo in that truck. 4lo shifting in the F250 isn't as pleasant in my opinion. The truck holds each gear too long (high rpms) and even manually shifting, it won't let you shift to a higher gear unless the revs are pretty high. I foresee using 4hi way more in the F250 than in the Tundra because of the shift pattern and because 1st and 2nd seem to be quite low even when transfer case is in high range.
Having 34 gallon fuel tank rather than 24 gallon tank has been huge improvement. I haven't yet recalibrated my head around that extra range when planning remote trail routes and so we ended up making one out-of-the-way drive for fuel when, in hindsight, it wasn't really needed. Having 30 useable gallons vs 20 useable is a huge improvement particularly since we've proven the 7.3L will get the same mpg, or better, than the 4.6L when the camper and truck are stocked for a week trip.
I mentioned it before, but also so nice to be able to drive decisively when loaded rather than very conservatively. Fullsize pickups required absolutely slowing down to the suggested curve speeds on highways where the Superduty easily handles the curves 10 - 15mph over suggested which is usually at the main posted speed limit.
Previous rig, the day-to-day handling was sound enough if driven conservatively, but I was always concerned about emergency maneuvers. I typically drove 100% of the time where with the Superduty, my wife easily and enjoyably took the wheel, for a couple hours on the drive down and back, on interstate sections with 80mph speed limit. Great!
More data: With camper on and towing 3,000lb fishing boat on our 150 miles loop to and from a local reservoir, I'm getting about 10.3 to 10.6mpg depending on how fast I drive (70mph to 75mph) and that days wind direction. That is the same mpg to a tiny bit better than the mpg of my previous 2013 Tundra with 4.6L V8, different camper but same weight, and same 3,000lb fishing boat. Very happy that the 7.3L lopes along while getting the same as the 4.6L V8 running about 3,000rpm in 4th gear (1:1) and 5th/6th locked out. Superduty runs mostly in 10th but will downshift to 7th (1:1) or 8th on the steeper interstate hills.
Really hard to ready exact rpm on the gauge, but the following is fairly accurate. This is 7.3L with 3.73 gearing and 285/75R18 tires.
65mph: 1,500rpm
70mph: 1,650rpm
75mph: 1,800rpm
80mph: 1,900rpm
