I Live In Missouri. The Truck Is An 89 E-350 U-haul Box Truck 17 Ft Bed. I'm Gonna Try To Make It A Little More Aerodynamic. I Also Have A Chance To Buy A 6.0 And Overdrive Out Of A Wrecked Truck, I Know It Has Alot More Power But I Don't Know How Much Better It Will Do On Mpg. I Have Talked To People With Power Strokes In These Trucks And There Ony Doing 10 Mpg. Is It Hard To Find A 3.08 Gear For The Dana 70.

 

I'm Sorry. I Haul Motorcycles To The Races And I Don't Pull Any Trailer.

 

Mine was getting about that same mileage - then the pump died. I wouldn't say it had "good" power with the old pump, but it wasn't so bad that I thought it was about to konk out on me. No smoking either. Just kinda' weak on the highway, and poor mileage. Figured that, based on the way everybody talks around here, the lack of highway power was pretty normal

Then the pump died. Pretty much lost ALL power. Still didn't smoke or anything though. I swapped the pump & injectors with a used set I had on a spare motor this last weekend and WOW! Feels like at least a 50% increase in power and my first 100 mile trip with it (yesterday) I got just under 14 mpg....

 

An F350 with a 17 foot box is a rather large truck. It is also a rather large wind sail.
I have a feeling that the rolling hills of Missouri, a truck that large with a natural aspirated motor and taller gears are not going to be a good combination. As for taller tires, you have dual tires on the back?
Increasing the tire height will be the same as going to a lower ratio gear, but on a dual wheel truck taller tires are usually also wider. If you run wider tires they may rub between the tire which will result in a blow out. You should have 235/85-16 tires, the only other tire I think you could run would be a 255/85-16 if you can find them. A 285/75-16 will definitely rub, so 285 or larger is out of the question without running spacers between the wheels which is also expensive.

The 6.0 motor is worthless unless you want to spend several weeks on wiring alone. Chasing down all the sensors, computers, wiring and changing everything you would need to change will make that a very expensive swap.

The mileage numbers everyone is tossing out are for pickups, not something like what you have with an 8 foot wide, 8 foot tall and 17 foot long box on the back.

If you got an overdrive unit like a Gear Vendors unit, you could split the gears, have an overdrive for when you could use it in high gear and probably pick up a couple MPG.
30 MPG, or even 20 MPG is out of the question and I think even 15 would be a far stretch. The Gear Vendors unit will be over 3000 dollars installed. www.gearvendors.com

 

With the price of fuel going thru the roof, MPG are on almost every one's mind,
Here's some suggestions

-open up your air intake
-install K&N filter
-bigger free flowing exhaust system
-have your IP & injectors tested
-use a diesel additive with every fill up
-use Duralube
-install propane injection
-keep your RPM's under 2100
Like I said, these are suggestions, I have done all of the above but the biggest MPG gain is in your right foot. lol

 

PLC 7.3 just posted this info out of a service manual.

Square footage of the vehicle front and the HP reqired to push it down the road at 55 MPH.

All this stuff came out of the 1987 7.3L diesel engine technician's update, which was used to quickly bring up to speed a 6.9 diesel mechanic. Also inside, was a chart which I found interesting. It shows the amount of HP required for a given frontal area at a given speed. I don't want to type up the whole chart, but I'll give you one column, for 55 MPH

Area in Sq. Ft. - HP required
50 - 56
60 - 66
70 - 78
80 - 89
90 - 99

So looking at this and figuring the frontal area just guessing 12 feet tall and 7 feet wide gives you 84 square feet. So looking at the chart I will guess you will use about 94 HP to maintain 55 MPH on flat road and no wind blowing. That is over half the HP of a 7.3 NA motor which is rated at 185 HP.

The more I think about your mileage and the vehicle you are driving the better I think your mileage is. I am only very slightly better with my pickup, if I keep it down to 60 I can get about 13 MPG. Load it up to 20,000 pounds and I am looking at 9 MPG.
Run it down the road at 70 MPH empty and I am in the 11.5 to 12 MPG range.

The hills are a little steeper here in WV and they are a lot closer together as well as longer. But that also means the chances of driving 100 miles with a constant head wind are a lot less.

 

Try an aftermarket turbo kit?

 

I've got an '87 with the 6.9l and 360000 klicks on it...just calculated my mileage last week and worked out to 23.4MPG highway...not bad for an old geezer.

 

i have an 86 f250 and get around 21 on the higway. 4wd and ats turbo

 

An 89 E350 with a 17 foot cargo box on the back.

Your pickup would almost fit in the box.

There is no way to get the MPG you could get with a pickup.

 

A good friend of mine is one of those gold wrench certified mechanics or something like that. He told me that there is not one thing that people lie about more than fuel mileage. Thats just what he told me because i go to him and ask how is that guy getting 35 mpg out of his 4dr 4 wd dually with 6500000000000000 miles!! up hill !! pulling a trailer!! just kiddin.I dont think i'm ever gonna get any better than 13mpg. my dually with a power stroke barelly gets that!! I'm also not gonna buy a turbo or overdrive i'd be better off to sell this and buy one with a powerstroke,and overdrive.

 

The truck in my signature has averaged 10.67 MPG this year. Worst was 8.27 MPG and the best was 13.5 MPG.

I load it heavy and drive it fast.
The engine was just rebuilt this summer to the tune of 4500 dollars for parts and machine work with me doing all the work.
Yes, I did a lot of extra things to get the power up.
The rings are just getting seated at about 8000 miles, the MPG is increasing every tank of fuel unless I am hauling something.

15+ MPG I have not seen since back in the days of high sulphur diesel when my average was close to 17 MPG. The last time I have seen 17 MPG was back in 1997.

My mileage numbers are very accurate, my speedometer is dead on and I get a cash reciept for every fuel purchase with the gallons on it, I write the mileage on every reciept.

Once you have a good database you can say what your mileage is.
The way the tanks fill, temperature variations, weather conditions, the fuel quality, winter blend, summer fuel, heavy loads, empty truck, your mood behind the wheel, idling time, long trip, short hops, lots of starts and stops all affect the MPG you will see out of one tank. Keep accurate records for 12 months and average it all together if you want to know what you are getting for mileage.

Stop and fill the truck at a station with the right front lower than the rest of the truck.
Next time you fill up have the left rear at the lowest point. When you figure the MPG, it will look like you are getting 20+ MPG. But the next time you fill you are back at the first station where the right front was lowest, when you figure that tank you will be in the upper single digits or very low teens.
Why?
Because of the amount of fuel that went into the tank alone. Both fill spouts go in the left side of the tank, the front tank is at the back on the left, so if the right front is downhill you can run in more fuel.

 

one other thing to think about if you realy want to get beter mpg, is to convert to a 5 speed, my 86 6.9l f250 4x4 (motor rebuilt a little over a year ago), get mid to high 20's (25 to 27) been keeping track since the motor was rebuilt. the only thing i can figger is my combo of 355 gears and a 5 speed tranny out of a mid 90's powerstroke.

 

we wont even need the batteries if you dont mind giving me a little push...

I would be interested to hear more about the 7.3's and 5 speeds, right now im waiting for my boss to decide what he wants for his.

 

man i love these fuel milage posts. i think i'm as cheap as cheaper jeeper. lol i have this 91 F350 with a 12 foot dump bed. the fool thing weighs 8000 pounds empty. i have a non turbo, so i have about 180 hp. the gearing is 355 rears with a ZF5 transmission. we calculated at 2200 rpm i would be going 70 mph. well 2300 rpm is all the engine will pull on level ground. i try to crruise at 70, but i know the engine is pretty much taxed. my milage is about 11 on the highway at 70. actually not so good. loaded and with a trailer behind it, the milage does not go down much. maybe 10 mpg, but will only turn 2100 rpm.