back on the MPG thing

[SWMO F-350]

1991 Ford F-350 Dually 4x2 with 5 speed and 4.10 gears.It has 167,000 miles with new injectors. 14 mpg at 60-65 mph empty 11 mpg at 60-65 mph pulling empty 25 ft gooseneck that weighs 5000 lbs 7 mpg at 45-55 mph with 6000 lbs on the trailer

[yotee]

4.10 gears

[joe f350]

i have 355 lol

[Chevy 6.2D]

Originally Posted by joe f350

put some sea foam it and change the filters it should get better

It has went thru a few filters, only have 500 miles on this one. I seafoamed it a few times, didn't seem like it did anything.
I thought about messing with timing, but was reading that if it sounds like a powerstroke while cold, it's probly set right- or at least close. It does sound like a PS when you start it in the cold (on the rare cold days it will start- LOL)

[lartross]

I've invested in a new injector pump, new glow plugs, rebuilt injectors, new fan clutch, new dual 2.5" exhaust with glass paks...and still get 14-16 mpg on the highway, unloaded running 65. I really envy those who get 20+. I'm thinking of getting an older Dodge 5.9 [94-97] to get the cheap power and good fuel mileage. I don't like Dodges, but, I want the power and economy. I've put so damned much money into this Ford...new AC system, steering gear, brakes, retrofitted hydroboost, alternator, water pump, trans cooler, tranny rebuild w/all upgrades...I hate to start over, but...I may.

[jhnlennon]

This will be my 5th IDI and I have never seen 20mpg's, not once. Most I ever got was 19 in f250 4x4, 3.55 gears, hypermax turbo straight 65 for 3 hrs straight. Average was more like 16, towing about 12-14. The only time I saw over 20 was with a 93 1st gen cummins 4x4 srw. I averaged 23 coming back from cody wyoming empty cruise set at 70, and the was a one time deal. Otherwise that truck was about the same for an average 16-17 in normal driving situations. My current cummins averages about the same with a high of 19 on straight hi-way driving. The 20mpgs and over in my opinion is a myth. I am happy getting 16 mpgs in a 8,000 pound truck. Heck, a new half ton doesnt get much better then that! Gasser 3/4 tons and 1 tons get half that at times!!

[FORDF250HDXLT]

Originally Posted by lartross

I've invested in a new injector pump, new glow plugs, rebuilt injectors, new fan clutch, new dual 2.5" exhaust with glass paks...and still get 14-16 mpg on the highway, unloaded running 65. I really envy those who get 20+. I'm thinking of getting an older Dodge 5.9 [94-97] to get the cheap power and good fuel mileage. I don't like Dodges, but, I want the power and economy. I've put so damned much money into this Ford...new AC system, steering gear, brakes, retrofitted hydroboost, alternator, water pump, trans cooler, tranny rebuild w/all upgrades...I hate to start over, but...I may.

what are you running for tires & @ what psi?
do you repack your wheel bearings every 40-50k?
did you lift each tire to see their not dragging?
sounds like you have a lot invested in the truck.you can set a cummins in theses rigs you know.people do it.
switching to an electric fuel pump $ fan will free up some hp/mpg as well as adding a turbo.the turbo being the greatest mpg increase.

ps yeah like jhnlennon says.these are some heavy trucks.16 is pretty dam good imho also! i will be absolutely pleased if i can average around 14-15.we do have to remember,these rigs where built to work,not ride around in.(i have a little 96 t-bird that gets average of 26mpg when i have no reason to haul something-this is the greatest mpg increase you can do-buy a small fairly decent car for your running in.-iv saved a lot of green doing this)

[lartross]

Stock tires, XPS's, 65psi empty, electric lift pump I've kinda' decided I want 4wd and crew cab [for our 4 dogs to travel in style! ha], so, I want to upgrade...just trying to think of the best possible upgrade I can do. I want to tow a trailer and travel some since we're now retired.

[David85]

Sounds like you've made up your mind then. While its true that these engines weren't really meant for MPGs, that doesn't mean they can't do it. My rule is now for 20 MPG empty if you can keep your RPMs below 2000 and cruise below 70 (whichever cruise speed is lower).

Frankly, 3.55s, E4OD, and 2wd is a great combo to get you there and I've seen other IDIs on these forums get high numbers. My truck can get 20 MPG cruise set @ 75 MPH if conditions are good and generally I don't really baby it either.

I'm not a fair judge for towing because I rarely move as much weight as some of the guys here.

There are many things that can pile up to keep you in the mid teens no matter how good you drive it.

Timing off,
Dripping injectors or poor injection spray (new ones sometimes do this shortly after install or in rare cases, right of of the box)
65 PSI is a little low, but that alone isn't enough to cause what you are seeing.
Short trips kill MPGs in these trucks
Thermostat opening too soon also kills MPGs

[lartross]

fairly new thermostat, 3rd IP, 3rd set of injectors...had em tested at a diesel shop...I have driven carefully, don't usually...but, no difference in economy. I wonder if the valves could be too tight...had the timing set by a pro...when I've been loaded, I get 10-12...which doesn't worry me too much, but, I have lusted after that 20mpg...maybe I'll get a power stroke instead of a dodge...I really like the 12v cummins, but, I know 7.3's a great engines also... time and the best deal will tell. Thanks for letting me chew my cud on y'all.

[pullinu]

Originally Posted by Dave Sponaugle

pullinu,
Welcome to FTE and the IDI diesel forum.

From my experiments with propane I have to ask,

If you total up the propane cost and the diesel cost, is your cost per mile any better than a lower MPG and running straight diesel?

I also got some huge increase in MPG whe I ran enough propane, but when I figured in the cost of both the diesel and the propane, I was right back where I started running just diesel.

You are right there is not any cost saving when your running a good shot of propane but the extra power sure is fun. Im new to this site but have run IDIs for years, reading some other replies of trucks never gettin more than 14 mpg baffles me, my stock 84 350 dumper with a 6.9 and a 4spd gets 20, there is not much to tuning these motors. I have never owned one that gets less that 20mpg, by the way does anyone have an opinion on what injector to run for max power out of a turbocharged 7.3 ?

[yotee]

moose misters. those injectors will give you the best spray pattern but at about $900+.

[Dave Sponaugle]

That good shot of propane can push the head gaskets right out of the engine, so be careful.

I very rarely ever get up to 14 MPG with mine.
Average for this year so far 10.89 MPG.

But Michigan is a lot flatter than WV is.

[David85]

Originally Posted by yotee

moose misters. those injectors will give you the best spray pattern but at about $900+.

Think the jury's stull out on that one. So far there is no confirmation that they get any better power or economy. Still waiting on another dyno run, but who knows when that will happen. In theory they should be way better, but until the observed numbers prove it.....I dunno.

[Knox]

1992 F250 7.3L 4x4
if i did it right i think i get 18 mixed highway and city