Just bought a 96 (10/95) F-250 Ext Cab with with 5.8L, Automatic 4X4 with 150,350 milies. I am still having some fuel consumption issues, I know it wont be great but is 12 to 14Mpg unrealistic? I am no stranger to Fords, however I guess I am stumped. Right now I am getting 8mpg. Over the weekend I changed oil and filter, new fuel, air, breather filters. Autolite AP24 Platnium plugs, NAPA Belden wires, Blue Streak cap and rotor. I noticed the engine ran much smoother, the previous owner had a birds nest of plug wire and the 7&8 were touching. I also hooked up the hot water lines back to the throttle body that were previously bypassed. Now the only thing I am wondering if the current tires 285 75R 16's would be hurting me on mileage? This is a Speed Density system. Any thoughts or previous experiences? The truck is super clean. There doesnt seem to be any brake binding.

 

The tires probably aren't hurting it that much. What gears does the truck have?

 

I have the exact same problem, I also have still have the spark knock problem. my tires are 265 and the thing gets horible milage. I am fixing to put it in the shop and have this friend of mine check all the sensors. Mine also seems a little down on grunt power. the engine runs great and smooth, just a little pluggish.

 

3.54 Gears in this truck

 

3.54 Gears in this truck. I am not sure if maybe running this some more and adding some Lucas Fuel Injector Cleaner, and then go from there. Anyone else have this problem? With a solution.

 

Hahaha
sorry

The ford 351 will not get much better then what you are getting now. Be thankful your not getting the typical 8mpg.
There is a saying for the 351efi...power of a 302, mpg of a 460.
It's mostly true. My carb 351 gets 2-3 mpg better then my efi and has more power while doing it. Get rid of the crappy exhaust and add some 1.7 roller rockers and you'll be happy. The cams are small and heads are made for a 302. It's very tricky to have an efficient combo on these engines and the efi hurts it more. I'm also sure if you had a custom chip made that it will gain mpg and power as well.

 

About this chip? explain more. adding MPG and power??? I have great respect for this engine first off. I have the 351W in my 95 E-350 and I get an average of 12MPG. I know buying a FORD, that I will not get great mileage. It seems to be getting better and I have some other minor things to work out however.

 

The aftermarket chips don't do much good . A dyno burned chip is good but expensive & are not needed on a mild motor , You can advance the base timing a few degess from 10 to 12-14 , that does about the samething as the chip but is free , underdive pulleys will help take some of the drag off the motor ...exhaust & 1.7 rockers work good to ....Lew

 

The factory timing curve on these trucks are horrific. Very lazy and safe.
I just checked my 351 mpg and I was 11.8 hyway 71 mph. So I actually bumped the timing up 2degrees(before I read this actually) and I'm going to run a tank of gas through it to check results.
Anyway, A generic chip won't help much on mpg, if you get a custom chip burned the Dyno tuner will optimize the whole power band, therefore increasing efficiency, which inturn help mpg and power.
Get a set of bolt in 1.7 roller rockers (unfortunaty require new valve covers as well I believe) and that will help with the small cam issue, then look into a less restrictive exhaust, chang o2 sensor also.

If you want better mpg you need to balance power and efficiency. New cam and heads and exhaust will do wonders.

Personally I don't like underdrive pullys because everything works slower, so your ac don't work as well and alt does not charge at idle as well. I'd rather spend money on exhaust.

 

Thanks for the info so far, I am quite capable of advancing the timing. I do own a light. On the exhaust, right now and this is how i bought it, they have the Large CAT with 4 bolt flange, a pipe, then going into a Cherry Bomb, and out the tail pipe in the back. I will look into the O2 sensor. I am driving it right now and it seems like the mileage might be getting better as I am running it.

 

If you advance the timing you need to do it with the spout unhooked when running
or you can advance the timing with the truck shut off but you can't really check base timing without The engne running and spout unplugged.
lots of directions onlne if you have not done It before