Fuel mileage

[FordGuy100]

I averaged right around 14mpg towing a 6500lb trailer from Texas to Oregon, usually doing around 65mph. Yours can do better.

 

[madpogue]

With 33s, you're actually getting a little less than 1 MPG more than what you calculate, since your odometer is about 7% off.

Batmobile - '85 w/Dealers Diesel rebuilt, 4x4, T19B, 3.55s, bone stock, 16-17 MPG mixed driving.

 

[Black dawg]

With 33s, you're actually getting a little less than 1 MPG more than what you calculate, since your odometer is about 7% off.

this, and you said "like 10mpg", have you actually calculated it.

and when you go to checking the accuracy of you odometer, compare the odo to mileposts, not the accuracy of the speedo.

 

[mjs2011]

Another way besides trying to count mile posts and compare distances, drive a long known distance and figure the difference between that distance and your odometer. It will be off by a percentage which compounds over longer distances. Or, use a gps

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[prepowerstroke]

No I havnt had it timed yet because I don't kno where I could have it timed a I went to my local international garage and asked them and they just laughed at me, saying that if I got rid of that old thing and bought a PSD I would be better off, so I left and have never went back but my truck has 4:10 gears which tachs about 2,000rpm at 60 mph and I have filled it up and recorded mileage and found out Percicley the mpg yet but I put fuel in it at when it's at half a tank (gauge is off so that's like 1/4 lol) I can't put 12gal in it and I can only drive about 120 miles before it's back to half a tank, I was thinking could I get super duty axles for a solid axle in the front and 3:73 gears?


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[prepowerstroke]

Have not filled it up and calculated mpg*


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[FordGuy100]

Your truck is amiss, regearing would be one of the last things I would consider. If you keep speeds around 60mph, your setup should do upper teens easily if everything is in working order.

Timing is important
Good injectors/spray pattern is important
IP Health is semi-important
Compression is important

Those are the big ones when it comes to FE on an IDI. Time to do a compression test and rule that out. Pull the injectors and have them pop tested. Get your IP timed.

 

[prepowerstroke]

New injectors have about 5,000 miles on them and truck rattles a lot like timing is advanced but I think the pump might be getting weak and trans is giving me probs with the torque coverter not wanting to stay locked in gear a shifting funny bought the kit to check compresson just haver done it yet, how much compression should it have?


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[mjs2011]

If you want to get it timed, PM Icanfixall, he rents timing meters so you can time the thing yourself. It is actually really easy with the tools he provides.

As for your mileage, are you sure you are driving those 120 miles, and is that in town or Highway take it on a drive some night on the highway, filling up before you go, then again when you return. Measure your distance traveled by following a route from Google maps, then do the math, miles driven / gallons added.

As for the axle swap, yes you will see some mpg improvements there, but I would focus in timing first.

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[prepowerstroke]

So I'll get a rebuilt ip and have it timed. But it's the idi suppost to have like 400 psi of compression?


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[FordGuy100]

IIRC 360psi is minimum spec. I would want to see 450psi personally. A fresh rebuilt IDI should do 500. All numbers should be within 10%

 

[Greg5OH]

thats odd, my old '84 with a banks turbo got about 20 hwy 15 city, and my '87 n/a gets about 15 hwy or city

everyone says these things get 20 mpg, im only seeing 16-17 on the freeway..dont get me started on in town. Definitly feels soft with old pump and injectors and no turbo with a crewcab. doesnt have OOMPH

 

[prepowerstroke]

Well I tryed to check compression with the tester I bought from harbor freight and the fitting it says to use for the 6.9 and 7.3 up to 1994 is too long it won't reach the treads so I found a shorter on in the box but the tread was a little coarser so I threaded it in a turn it two till it got trying not to mess up threads in the head on the drivers said front cylinder and I cranked it you could hear alittle bit of hissing but I cranked it till th needle stopped coming up an it landed at 350


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[mu2bdriver]

everyone says these things get 20 mpg...

At 60mph, I'm getting about 20mpg at around 2100RPM.
At 65mph, I'm getting about 17mpg at around 2200RPM.
At 70mph, I'm getting under 15mpg at around 2400RPM.
I don't stomp on it, I let it smoothly upshift, it rarely gets above 2500RPM, and I live in the right lane.
Around 95% of my driving is highway driving, half is nighttime, and half is off-peak so I'm not clogging the roads.

1991 F250 E4OD 4.10 NA

 

[Shadetreemechanic]

Well I tryed to check compression with the tester I bought from harbor freight and the fitting it says to use for the 6.9 and 7.3 up to 1994 is too long it won't reach the treads so I found a shorter on in the box but the tread was a little coarser so I threaded it in a turn it two till it got trying not to mess up threads in the head on the drivers said front cylinder and I cranked it you could hear alittle bit of hissing but I cranked it till th needle stopped coming up an it landed at 350


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you can adapt the HF adapter so it will work. Just remove the valvestem in the end, cut it down with a hacksaw using a glowplug as a template, reinsert the valve stem and its good to go. My memory is that the correct length has the valve stem end just sticking out of the adapter. I have a thread on here somewhere about fixing the Harbor Freight compression adapter.