I'm over 18k miles on my truck now and I was towing my 5th wheel down I-5 just cruising along at 60mph and
glanced down at my Trip to see I was averaging 9.2mpg according to the lie-o-meter. After 120 miles I unhooked and drove a mile to Costco to top off and I kept pumping after it clicked off to round up and I hand calculated 8.6mpg and the dash said 9.2mpg.

I drove a 440 mile loop empty 2 days ago and my speed was between 60 and 70mph most of the time with a few towns with stop lights every 50ish miles where the speed dropped as low as 30mph a few places. There was a max of 2000ft elevation change on the route and my average for this tank was 14.3mpg when I filled up at Costco the next day. I eked out 15.5mpg on a tank in northern Arizona around 7k feet with my cruise set at 66mph.

I'm now getting better fuel economy when empty every tank than I was with a 3.73 truck. I'm pretty impressed with the fuel economy out of a 4x4 crew cab dually with 4.30 gears and 31.5" tires. My 6.0 dually could get 20mpg empty at 70mph but once the turbo was making double digit boost my fuel mileage was in the single digits. That motor would run all day at 14-18psi while towing my 5th wheel and 8mpg was average doing 65mph and never exceeding 70mph.

The only place I cant beat the fuel economy numbers from my old 7.3 gas truck is stop and go traffic, I'm 10-11mpg and that truck was 11-12, and towing where I am still .5-1mpg lower with 4.30 gears.

I turned traction control off and drove almost 200 miles yesterday in everything 70mph to gridlock and it did smooth out my 1-3-4 and down shifts. So much so that I watched the gear indicator while slowing down and the 3-1 downshift couldn't even be felt at all. I turned off Advanced trac and could tell any difference between just traction control and advanced trac being off. My 6-5 downshift was more noticeable with these off than driving in Normal or Eco.

 

Nice write up! Same here. What Mode your in for the driving you doing is so important! Stop n go/town/grid lock empty 10-12 mpg. 71 mph with 4.30 gears is my sweet maxspeed/max efficiency @ 14-16mpg. Towing 14k at 5000 elevation 8-10 mpg.

 

I would love to see the mileage this exact engine/transmission combo would do in a panther platform for fuel economy. My 94 Town Car averaged 27mpg at 70mph with a 4.6L and 3.31 gears I believe. I got 40mpg on a 45 mile stretch of mostly flat road outside of Carlsbad, NM. The DRW with 4.30 gears will shift into 10th gear by 36MPH and you can get the torque converter to lockup between 40 and 45mph. Once you achieve lockup your MPGs are insane for a motor this size in a truck this big.

 

Mileage in these trucks are pretty impressive. Just did 452 mile trip from Custer, SD to Hasting, NE for work 15.99 mpg (hand calculated) cruise set at 68 other than the small towns on Rt2 to slow down through. Not bad for 8,800# truck.

Dash lieometer was reset before leaving and was giving major unicorn display reading of 17.4 mpg. Usally it's off by 2/10 - 3/10s.

 

Just did a road trip today to put on some break in mileage on the new 23 dually. Started the trip with 149 on the odometer ended with 515. Averaged right at 14 mpg. Speed limits were from 55 in the mountains to 80 on the interstate. I have 4:30 gears. Pretty impressed so far. Also never dropped under 8th gear on the passes, up to 7%

 

My observations are WIND is a deciding factor (interstate highway driving) in mpg most of the time, all else like speed, load, road, and trailer being equal. Even a gentle 15mph headwind will cost me significant mpg.

Once when starting westbound out of Amarillo, TX, a sustained 40mph wind came straight at me for the next tank full of fuel. MPG went from 14.2 to 9.5 the entire way into Arizona.

On the other hand, a tail wind will give mpg a small boost. Side or front diagonal winds reduce mpg.

 

My mpg has never improved since day one. I was getting good mileage that day and still do today, has not changed appreciably up or down in 66,000 miles...

 

My other 7.3 only had a slight bump in mileage over 20k miles. I was getting 11mpg at 65mph when I first bought this truck and it made me really bitter about getting 4.30 gears. It still gets worse towing and in stop and go than that truck but on the highway I never consistently got 14+mpg with the 3.73 truck. Now it is anytime I'm driving 60-75mph I can get 14mpg or better.

I towed from The Wall outside Badlands all the way to Ashland, NE with a 30mph tailwind cruising at 70-75mph in 10th gear and I averaged 8.5mpg for that whole trip. Once I turned south it was a crosswind but I got such good mileage to Sioux Falls that it still averaged that good.

 

I'm in the same boat that the truck from day one was getting great mileage and hasn't changed. My problem is keeping the foot out of it when doing long drives and trimming some time. Then the mileage will drop but still in the 14-15 mpg. I don't know about anyone else but the 7.3 was purchased for the hp/ tq not the mileage which is a plus equaling the 6.2 it replaced. 😉

 

Sometimes it is about making time and fortunately you can with the 7.3 I rocked a trip to SLC a couple weeks back to haul a machine for a friend. The goal was to get it done in a day, 750 miles. I was running 80 mph on I 70 both ways and still got decent mileage. My 7.3 truck does a solid 2-3 mpg better than my steel body 6.2 6 speed truck did and it pulls better. Certainly no complaints here.

Yesterday we took a trip over the mtn to Silverton, then a trip back into town, right around 17 mpg for that 150 miles. Problem is, the truck is so good all around that we take it everywhere and use it for almost everything.

 

Very good info guys. I only have 5000 miles on my odometer and have pulled 90% of those miles. My last 7.3 improved from 12 to 14 after 10,000 miles on the highway empty. I'm kind of excited to see if that holds true on my '22.
Hey Scrap, I didn't know you were in my neck of the woods.....

 

This wasn't done on purpose, got distracted with work business before realizing I probably should of topped the tank earlier in the drive. Coming through the sand hills in NE when the 50 mile to E showed. It was either 15 miles backwards or 45 miles in the direction traveling towards Alliance. Figured to roll the dice. This is pulling into the gas station.



The 34 gallon tank took 32.98 gallons. Not much buffer of 1 gallon in the tank which would be roughly 15 miles.

 

The first truck I bought had 3 miles to empty and the salesman asked if I wanted to test drive it. I asked "To the gas station?" And he looked at the gauge and sent a porter to top it off.

 

I almost never go through a full tank without towing since I can go 600+ miles to a tank but I made a trip to town from my boondocking spot. 50-60mph, 1000ft elevation, flat, no wind, 83F. Advance trac off and driving in Normal mode. All 6 tires are at 60psi nothing in the truck or bed. Then I did a round trip to town and back at a new spot at 600ft elevation 74F almost no wind.

I still get 6.5-7mpg towing my 5th wheel

 

We did a short run up to OK, from Dallas, last week, with my standard load of junk in the back... about 800#... and averaged 16.6mpg at 70-75mph. Nothing super-duper, but I can tell the mileage is improving a little since my trip to IN back in June. I don't yet have 6000mi on the clock.

We're fixing to head out to NV next week, so that will be a really good barometer of what the engine will do... a mix of flat and mountains, and altitudes. I will likely have the same load out... not work junk, but our travel stuffs. Where I was lucky to get 13mpg with my 6.0L 2500HD, I expect to average 16mpg for the trip. We will see...