1999 7.3 powerstroke bad mpg

[lindboep]

I have a 99 f350 with a 7.3. Driving on thr interstate at 71mph 2250rpm I get 8 mpg.....is that normal? I have 4x4 truck has 110k on it

 

[clutch]

that was normal for my '74 F250 with a C6 and the 460, lol.
Maybe you could give us a little more info, how long have had this truck? Has the fuel mileage always been like that? Auto trans? Oversize tires? Gearing? What happens when you cruise at say 60 mph? And are you empty/no load?

 

[lindboep]

that was normal for my '74 F250 with a C6 and the 460, lol.
Maybe you could give us a little more info, how long have had this truck? Has the fuel mileage always been like that? Auto trans? Oversize tires? Gearing? What happens when you cruise at say 60 mph? And are you empty/no load?

Had it about a month always been like this. Auto tranny w/ overdrive. Normal tired and yes empty no load. It is a dually

 

[clutch]

hmm, yeah, I don't know, my '93 IDI single rear wheel, 4x4 w/5sp gets around 15 mpg. How are you calculating? I always reset the trip odometer when I fuel up, and then on the next fuel, up divide miles by gallons.
Only a guess but maybe brake drag somewhere...
Prolly be somemore folks logging on tonight that could help...
Welcome to FTF.

 

[lindboep]

hmm, yeah, I don't know, my '93 IDI single rear wheel, 4x4 w/5sp gets around 15 mpg. How are you calculating? I always reset the trip odometer when I fuel up, and then on the next fuel, up divide miles by gallons.
Only a guess but maybe brake drag somewhere...
Prolly be somemore folks logging on tonight that could help...
Welcome to FTF.

Divifing miles by gallons. If I go 60 I get 12mpg

 

[blacksnapon]

Any smoke from the exhaust? Do you gain oil in the pan? Any misfires?

 

[lindboep]

Any smoke from the exhaust? Do you gain oil in the pan? Any misfires?

No smoke from exhaust. No misfires. What do you mean do I gain oil? At idle I do notice it makes a weird noise. Almost like it struggling for air but then back and it does it like every 15 seconds

 

[clutch]

pulled the air filter yet?
couple used ones I looked at had mouse nests in the air box.

 

[blacksnapon]

No smoke from exhaust. No misfires. What do you mean do I gain oil? At idle I do notice it makes a weird noise. Almost like it struggling for air but then back and it does it like every 15 seconds

Smoke from the exhaust.....injector slobbering raw fuel. Misfires.....injector, or bad cylinder. Gaining oil.....internal fuel leak going into the pan increasing oil level. That leaves air intake obstruction, low gears, and a few other off the wall issues.

 

[lindboep]

pulled the air filter yet?
couple used ones I looked at had mouse nests in the air box.

Air filters clean. Also ivr noticed it seems sluggish compared to other diesels ive driven. Doesn't have very much power and has a hard time getting over 65 when towning my small fishing boat

 

[clutch]

yeah, again, hard to really say...
Didja watch the video on how to change the fuel filter?
lol, just watched it, doubt that could entirely be the problem,
but my only other suggestion is a bottle of Lucas Injector cleaner,
maybe a fresh oil change, check all fluids, air pressure in tires,
ya know, just the simple easy stuff, for now. And look at those brakes, I've heard of calipers sticking, and I had an old rusty Toyota that the parking brake rusted in the on position, lol. Had to take a hammer to it, and the brakes Good luck, I have hope for you since you say the mileage does increase when you roll a little slower.

 

[lindboep]

yeah, again, hard to really say...
Didja watch the video on how to change the fuel filter?
lol, just watched it, doubt that could entirely be the problem,
but my only other suggestion is a bottle of Lucas Injector cleaner,
maybe a fresh oil change, check all fluids, air pressure in tires,
ya know, just the simple easy stuff, for now. And look at those brakes, I've heard of calipers sticking, and I had an old rusty Toyota that the parking brake rusted in the on position, lol. Had to take a hammer to it, and the brakes Good luck, I have hope for you since you say the mileage does increase when you roll a little slower.

I have a new fuel filter in my truck. I know how to just haven't had a chance to try

 

[lindboep]

yeah, again, hard to really say...
Didja watch the video on how to change the fuel filter?
lol, just watched it, doubt that could entirely be the problem,
but my only other suggestion is a bottle of Lucas Injector cleaner,
maybe a fresh oil change, check all fluids, air pressure in tires,
ya know, just the simple easy stuff, for now. And look at those brakes, I've heard of calipers sticking, and I had an old rusty Toyota that the parking brake rusted in the on position, lol. Had to take a hammer to it, and the brakes Good luck, I have hope for you since you say the mileage does increase when you roll a little slower.

Also if I tow at 70 or well even drive at 70 with overdrive on it red lines. Is it maybe not shifting into the last gear?

 

[clutch]

man, IDK, but sounds like a very reasonable assessment... I recall speaking with a Ford mechanic who said those overdrive gears won't stand up to a a lot of abuse. Hopefully you are not due for a rebuild, but it seems likely.
my only suggestion would be to flush and fill with fresh ATF, and see if that helps. But I'm no mechanic! lol Hope a few others will chime in, hang on...

 

[blacksnapon]

Yup, sounds like you need another gear. Its definitely overrevving.

 

[Mustangranch22]

I have personally always noticed on the 3 different powerstrokes i have had that 2000 RPM is the sweet spot for fuel economy. when you run over that regardless of auto or manual trans the mileage goes downhill fast.

Very hard to run down the interstate at 2000 rpm's without getting run over though