Fuel Mileage

[spencergt66]

Just a couple questions I just started to drive the beast to work and i noticed that I likes to suck down the fuel Yea i know that its a big truck but the last diesel i had got around 19 mpg (Chevy 6.5 4x4 2500) Just wondering what everyone else is getting for mileage in a similar size truck also is there anything you guys did to make an increase in mileage? any way just curious not complaining about anything O in case I forgot to mention I'm getting 12mpg

 

[jperecko]

There are several mileage posts floating around. the basics are get your timing set right and lower gears with a manual tranny will yield the best results. I see you have a ZF5 so you are good in that department. You likely have 4.10 axles. Maybe swap that or get taller tires. Oh and drive sensibly.

 

[icanfixall]

Well... Mels son repowered a 94 F150 with a 6.9 and it gets 31 mph.... The truck weighs in at 3200 lbs. The chevy diesels always got great 20 + mph as compared to our 6.9 or 7.3 motors getting 15 to 18 mpg.

 

[jperecko]

Well... Mels son repowered a 94 F150 with a 6.9 and it gets 31 mph.... The truck weighs in at 3200 lbs. The chevy diesels always got great 20 + mph as compared to our 6.9 or 7.3 motors getting 15 to 18 mpg.

Think you mean MPG there... sure hope it does better than 31 MPH

 

[ameristar1]

Agnem's son has a 6.9 powered F150 that is getting in the high 20's, there is more specific info on one of the threads that explains the exact settup.
The thing about the IDI's is that when the fuel system needs freshening, it lets you know in a big way performance wise. Just doing the pump, injectors and giving it a proper tune will get the mileage up quite a bit.
Another thing to try is some Auto Rx run through the motor. Just getting the piston rings free and restoring lost compression will bring the mpg up. If you have more than 200k on the motor it'll take a couple of clean/rinse cycles, but the results are worth it.
Shifting too high with this motor, unlike the 6.5 GM, will make it **** the fuel out the pipe. You have to literally drive it like a semi if you want good mileage. Try progressive shifting, if you're not in a rush, keeping the changes around 1500-1700 rpms and see what happens.
On average, depending on the combo and driving habits, folks have seen a low of 11-13mpg (low gears, no overdrive in the trans, the C6/4.10 probably the worst), to almost 30mpg (the light truck, tall gears, modified pump, manual trans).

 

[Hyde]

With a c6 and 3.55's I get about 14mpg. I think they are 3.55's judging by the kids on trikes that beat me off stop lights. This is with 33's, pump turned up and I drive it like a Detroit.

 

[spencergt66]

Well like all the diesel trucks Ive owned with a manual trans I try to keep the rpms pretty low down the freeway though on the way to work It runs at 2200 going down the road. I just put in some new gauges ( boost and pyro) and the numbers didn't seam too bad but i would have liked to see some more boost on the test drive going down the road with my foot in it getting as much load as i could i only got 7-8 psi of boost and 1150 F on the pyro driving normal like I usually do, like a grandpa, i get around 800 on the pyro and 4-5 psi boost i haven't done anything to the engine the pump was replaced before i bought it the only thing i have done to the truck is get the exhaust leaks fixed, install a 5" exhaust no muffler with a 3" down pipe and I made a new intake for it due to the factory one pretty much falling apart the truck only smoke a bit when i shift if I'm accelerating up the road but driving normal through town there no smoke at all or vary little the truck seams to run pretty good the only thing i noticed is that around 3000 rpm or right after it just falls on its face im assuming thats where governor starts pulling fuel away but never had one quite act like that but the truck is new to me so I'm just getting all the bugs worked out so to speak

 

[Diesel JD]

Well I wouldn't expect it to get the fuel mileage of the 6.5, but I'd think 14-16 in town and 18 on the highway would be reasonable to expect. Even with no O/D I get 12-14 in town on B100 and 15-17 on the highway. I also know the pump timing is retarded and I have leaks on the return side. You say the pump was recently replaces but how about the injectors? Also the pump timing could be off and if it is that could cost you a MPG or 2 or more depending on how far off it is and in what direction.

 

[Mat J]

just wondering but why dont we get closer to the MPG as the older detroit idi's? Is it all mainly in the gearing?

 

[Hyde]

The detroits were built for economy, our engines are heavy duty engines in a light truck

 

[Alex S]

my 91 F-350 CC 4x4 zf5 7.3 na gets 20 mpg on the highway, but i stay to the speed limet (thats the trick) 2200 rpm constant

(i have a 200 km round trip to work)

 

[needboost2live]

when i first started driving my truck i got 15..... by the third tank of gas i am getting 17 mpg. My truck is 94 factory turbo with a reman 7.3 IDI with about 35,*** miles. I have an E40D and i believe 4.10 in the rear. I drive like a grandpa (have to cause the tranny is banging gears) and that could be the reason for the decent mileage. Grandpa = nothing over 65 cause it starts to kill the mileage, slow accel (as to not kill the tranny), light foot.

 

[FordGuy100]

Well I see you live in Texas. That means you drive what...like 120mph? Sorry its a joke I have with some people I know there. Speed kills these trucks. My truck lately has been getting 18.5mpg...I just really wish I had an overdrive of some sort, I'm sure I could get into the low 20's if I did. But I dont go over 65mph

 

[david85]

What is your distance and average speed on your drive to work?

How many miles on your injectors and injector pump?

12 MPG is way too low. Only time I ever see numbers that low is when I am towing our boat across town several days in a row (lots of cold starts, and stop and go traffic with the tall gears). Even then, I rarely drop below 13 MPG like that.

Today I was towing at 60-75 MPH while averaging 70 and up most of the time. Calculated 14.5 MPG when I got home.

 

[ameristar1]

just wondering but why dont we get closer to the MPG as the older detroit idi's? Is it all mainly in the gearing?

I have wondered the same thing also, since the GM and the Navistar use the same injection system, have the same compression ratio (roughly). I see the obvious things like the gearing and weight. The way the pumps are set from the factory don't help the situation with the 6.9/7.3 either. If Agnem's pump guy showed anything about the Baby Moose, it can mpg well if the tuneup is right.
But one thing I believe makes the 6.2/6.5 mpg way better than the IH is that the precups are designed with high mpg in mind from the getgo. There's an article on the Diesel Page that talks about the differences between the N/A and turbo precups for the 6.2/6.5 and how that one thing caused the economy to drop something like 4-6mpg for the turbo motor. Trucks that used to get 22-23mpg now were down to 16-17mpg (turbo 6.5/stock tune).
I wish Ford made an option for max economy (3.08 gears and taller with skinny tires on a half ton chassis).