MPG major loss?

Jkk7_3

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I have a 1995 f350 7.3 extended cab dually, 2wd, the truck has gotten about 10mpg for the past many years of its life unloaded, I see exact same trucks, extended cab dually 2wd 7.3's getting 22mpg. Multiple buddies of mine have highly lifted 4wd vehicles getting 21-22mpg, and I don't understand why or how their lifted 4wd 7.3s are getting so much better mileage than a 2wd stock height 7.3, it's been getting this type of mileage since it was completely stock. Any input is appreciated on what it could be, I'm thinking possibly pcm, as the truck has had previous serious electrical problems. Could it be pcm? Anything else?
 

dsberman94

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Mine doesn't touch 20 without hours straight at 65 on the highway. And mine is newer and stock height. I think your buddies are full of it. Also are they doing the math to change the mileage to account for the larger tires im sure they're running?
 

Diabolic

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I have an auto with 4.10 gears and 35" tires. At 70mph I'm turning about 2200 rpm. If I set the cruise on 70mph and run 95% hwy, I get 18mpg. If I do almost all in town, I'll get 14mpg driving normally. I have a 4" exh, 3"DP, e-fuel, 160 injectors, TS chip, and Tymar filter.
 

Jkk7_3

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I have an auto with 4.10 gears and 35" tires. At 70mph I'm turning about 2200 rpm. If I set the cruise on 70mph and run 95% hwy, I get 18mpg. If I do almost all in town, I'll get 14mpg driving normally. I have a 4" exh, 3"DP, e-fuel, 160 injectors, TS chip, and Tymar filter.

I have a 3indp 4inexhaust 160/80 injectors t500 efuel intercooler d66 and I get 11 so pretty much same setup as you, and I have never seen 18 lol
 

superpsd

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I seem to get 16-18 average. I have seen as high as 20 out on the highway. 3.55s and a ZF so I'm turning 2000 @ 70mph. That's with 350/200s my mileage didn't change really from stock sticks. It's hard to keep track as I'm always making changes. However I drive my same daily route so I have a feel for if it starts to use fuel quicker.
 
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Diabolic

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Maybe your speedo is off so your mpg calculation is too? Maybe you have a fuel leak somewhere? Perhaps the tune is off for your injectors?
 

mikeeg02

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I have a 3indp 4inexhaust 160/80 injectors t500 efuel intercooler d66 and I get 11 so pretty much same setup as you, and I have never seen 18 lol

But what size tire ? Stock 265/75-16?

Rpm differences are pretty big from 32" to 35"

The key to happy fuel mileage on a 7.3 is generally 2,000 rpm and under. If you can handle cruising at 1800-1900rpm. That's usually the we sweet spot. Usually.

This time of the year, we also get winter fuel. For example, two weekends ago I drove from PA to Richmond VA. I got 14.5 on the way down, got fuel there, and 16.5 on the way up.

I run 235/85 tires on 3.73s though. (Dually)
 
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Jkk7_3

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My mileage never changed from stock to 160/80 either, remained the same, and nope no fuel leaks, speedo isn't off, stock size tires, tunes aren't off for the truck, have had it retuned twice, also when the truck was completely stock it was getting 10-11 mpg as well. Nothing I've ever done has changed it, don't know why it's so low, would like to go to 3.73 gears eventually that should help a little but I don't know what else i could do or what else may be wrong
 

mikeeg02

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Being that youre in new jersey, is it.mostly stop and go, in town traffic ? Or do you get to go and stay on the highway, and rural routes ? Doing your best to keep it under 2k rpm helps
 

Jkk7_3

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Stop and go as I'm sure you've been in nj and know, If I do get to go on the highway it is as well stop and go. Too many people.
 

mikeeg02

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Thats what i was afraid of. Stop and go kills the mileage on any vehicle. I think you'd find it did better on a trip. I'm not sure you're going to do much better. I've heard there are some rural areas of Jersey, just haven't seen them haha
 

Jkk7_3

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I used to live in the rural south of New Jersey, but now I am in the central stop and go area, can't go more than 10 minutes without having to stop on the roads by me, but thank you all for your input, highly appreciated!
 

Lt.Dan

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What if its not anything motor related? What if its the brakes dragging? Or something similar. Just throwing ideas out to get everyones mind rolling.

My 96 will get about 14-15 city, and 16-17 hwy. With Auto/4.10s and 34" tires, stock height, 2wd.
 

Jkk7_3

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Brakes don't drag, if it was something obvious I'd see or smell it, figured it might have been an electrical problem but no one seems to think so
 

crcrawford87

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Sounds like your problem is related to the area you drive in, stop and go will kill mileage worse than anything. Getting a 8k truck moving from a stop takes a lot, if the engine doesn't get to operating temp while driving that can cause major mpg losses also.
 

Diabolic

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I just got back from a 500 mile unloaded trip. Kept the cruise set most of the way with the tach at 2000 rpm. I got 16.8 mpg. That was with slow traffic in Ft Worth.
 

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