2003 7.3 E350 box truck with a 14' box and 4.10 DRW. Last 600 mile round trip I got just about 12.0 mpg driving 65 - 70 and going from sea level to 5,000' and back again. I've put about 4,000 miles on this rig since I bought it a little over a year ago and it looks like my average has been just over 10 mpg. My best mileage was 13.4 bringing her home when I bought her 450 mile away and running empty other than my 700lb. Fat Bob in the back. All of my trips, excluding the last one where I maintained 65 - 70, were running the speed of traffic which was probably closer to 75 - 80. My projected frontal area is basically 8' x 10' so imagine pushing two sheets of plywood perpendicular to the wind at 75 mph. It would be interesting seeing what kind of mileage I could get at a steady 55 but thats not likely to happen as long as I'm on the interstates. Loaded, which is the only way the truck gets driven, I'm at about 6 tons. There's no free lunch. Otoh, the van serves as our camper/toyhauler, has plenty of headroom to stand and walk around, eliminates dragging a trailer around, and we can comfortably sleep inside while fully loaded with two road bikes and all of our gear. Modifications follow every trip and it just keeps getting better.
On our last trip we got 16.7L/100km (~14mpg). That's weighing in at 3,530kg with the bubble roof. In this neck of the woods every trip starts off with a gnarly headwind through the foothills and numerous mountain passes. This particular trip also included a "quick" 20km jaunt up a 800m fire road so I was pretty happy with that mileage and it's close to the best we've ever gotten. Normally things are closer to 18L/100km. For comparison, our Crosstrek on day trips gets at best 8L/100km (~30mpg) and I'm a speed limit kind of guy.
Some of you must have some seriously flat roads to get the mileage you do!
Oddly enough, my best logged mpg was on a narrow, winding, mountain highway in a snow storm. It was about 100 miles and went from sea level to the summit at 1156 ft and down to sea level with a few ups and downs along the way.
The Turbo was on hiatus, speeds were steady but slower, no quick starts or stops. I by the fuel used I saw 11 L/100 km (21.38 mpg). From a rig with a big box weighing 9600 lbs. Its corners on the top have a 6” radius... and it’s frontal surface is 88” with and it’s about 102” tall. Unlike a standard box truck, it spent time in a wind tunnel during its design phase.
The moral... the more you push the pedal... the more it’ll drink.
The best I’ve gotten on a complete tankful is 35.5 MPG in adiesel Grand Cherokee — all highway driving, at reasonable speeds and little wind (tail or head). I went 835 miles on that tank. Wish my bladder could last that long.
2004 Ford V10 E350 eb SMB. Quigly 4wd and fixed high roof. On the 1100 mile trip home to Oklahoma from Virginia, I kept the speed averaging 65 mph. Worst tank 12.7mpg. Best 13.8 mpg. Water and fuel tanks were full, but we hadn't loaded any other gear yet. We just had new bumpers built, and have gone to larger tires, so I expect those figures to drop.
It's good to know it wasn't an aberration when I got a 21mpg tank.
1999 E350 EB high top 7.3 PSD:
2 wheel drive 3:73's and stock tires: 16-21mpg
4x4 with 6" lift and 3.73's with 35's: 14-16mpg
4x4 with 6" lift and 4:30's and stock F250 wheels: 14-15mpg
4x4 with 6" lift and 4:30's and 35's: 13-14mpg
4x4 as above towing a 6000lb trailer: 10-13mpg
I've tried many things to improve the mileage and I've come to the conclusion that 14 is what I get.
As an aside here's the rig it replaced:
2003 Ford 4x4 F150 Supercrew 5.4:
Stock wheels/tires: 14-16mpg
33" tires: 12-14mpg
towing the same trailer: 6-8 mpg
With the larger tires and jank added to the roof of my van I lost about 1 mpg on the hwy. Of course into the wind the drop is more. My van does have the full dpf exhaust cleaning suite so when it goes through a regeneration mpgs drop dramatically. Best I've done since I added all the stuff was 19 mpg on a trip from Northern Washington back to Eugene one day. Mostly all freeway driving of course. The worst I ever see is about 16 on the freeway and thats cranking at least at 75. The wind makes a huge difference of course on these things. Mine has a 3.54 rear end which helps to keep the RPMs down a lot as compared to my E350 which had a 4.10. I don't hit 2000 RPMs now until over 70 mph.
I, like many, love to track my mpgs but mostly out of curiosity. I averaged 16 on our last trip from Eugene, then toodling around the Jackson Hole/Teton Valley area for a week, up through Yellowstone, then across the reclamation road from Flagg Ranch to Idaho, then on to Sun Valley and back to Oregon. I felt fine with that, but I don't really consider MPGs to be a deciding factor in much considering that I drive a 4 ton 4x4 rig with lots of hauling capability. Its nice to get great MPGs of course, don't get me wrong, but it would have to be pretty awful for me to consider a different rig.