Fuel mileage numbers?

[FORDF250HDXLT]

The more I read this, the more irritated I get....I usually get 11 city no matter how I drive it. I know I'm well due for an IP and a set of injectors(plus I could use a return line kit) but geez. $4.19/gallon sure does hurt.

i know how ya feel brother.i seem to be on a downward spiral myself.getting lots of lower teen results lately.
i ordered some new Stanadyne factory turbo G codes last night to replace my BB code remans.i sure hope this helps her out.
i also need to swap to the turbo ip for it's better timing curve.i hope that helps too.
i ordered new timing equipment which i hope helps.i guess my old mag pickup was starting to give false reading right after the turbo install,and i just didn't know it then.
today i finished up sliding out my under body toolboxes so i can enclose between them/over the wheels, to cover the gaps.this should help a lot to keep the air flowing smooth to the back instead of getting trapped under the bed.
with fuel on the raise,and coming up from already insane prices,we simply can't afford to mess around.

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you know,something i forgot to add.i'll edit it in sometime.when i swapped in my true DRW axle (which i want to keep good) i then went to recommended thicker synthetic gear oil.
i was running the thinner mobil 1,and now their thicker.whatever those weights are.i'll look it up and edit that in.i ran old school stuff for first couple tanks actually to just cheaply (well,less costly) flush it out first.

i might go back to the thinner and just let the ring and pinion ware.with these fuel prices,that might be the much cheaper solution now.sad isn't it.

 

[PwrSmoke]

The question was asked whether the odo has be recalibrated for the larger tires and that will be one of the keys to this. The speedo is calibrated for a 33 inch tires (with a 33 my odo is dead-nuts on). With the stock 31, it's off by just under 10 percent. As far as I know all the bullnose trucks are the same in that regard and the error leads to MPG readings that are better than actual (shows more miles travel than actual and shows more speed than actual).

Tire tread, rolling resistance, makes a HUGE difference in MPG. I participated in a test that showed a 2.4 MPG difference between an all season tire and a mild mud terrain tire (or an aggressive all terrain... you pick). THey are just now starting to run rolling resistance tests on light truck tires. The ones published so far show a big increase as the tire treads get more aggressive.

 

[FordGuy100]

Agreed, with 285's my speedo is spot on now.

 

[vanet]

The key to getting good mileage with these trucks is to keep the RPM's as close to 2k as possible. With my zf-5 I can run 60 and get 20-21 mpg, rpm is exactly 2k if I bump it up to 65-70, mpg falls to 18, rpms go to 2400. Speed doesnt seem to matter, as long as you keep the engine around 2k. Get much above that and mpgs start droping off fast. This truck has street tires. My wheeling truck has 35" bfg mud terrains with a c-6. However if I keep the rpms around 2000 (which means around 52 mph with out overdrive) I still get around 19 or 20, even with the mud terrains and the automatic both of which lower mpg some.

 

[Black dawg]

The question was asked whether the odo has be recalibrated for the larger tires and that will be one of the keys to this. The speedo is calibrated for a 33 inch tires (with a 33 my odo is dead-nuts on). With the stock 31, it's off by just under 10 percent. As far as I know all the bullnose trucks are the same in that regard and the error leads to MPG readings that are better than actual (shows more miles travel than actual and shows more speed than actual).

Tire tread, rolling resistance, makes a HUGE difference in MPG. I participated in a test that showed a 2.4 MPG difference between an all season tire and a mild mud terrain tire (or an aggressive all terrain... you pick). THey are just now starting to run rolling resistance tests on light truck tires. The ones published so far show a big increase as the tire treads get more aggressive.

From what I have seen, the odo is correct with the stock 235/75-16 (32.7" I think??) and will be a little more than10% slow with 315/75-16. I know lots of people that think that since the speedo is right on with the bigger tires that the odo must be correct also. The speedometer needle doesnt have a direct connection to the speedo cable and usually reads 3-5 mph fast with stock size tires.

 

[Blind Driver2]

I'm getting 17 mpg in the city. I don't know what the highway figures are. I know my timing is off as I haven't timed it after putting in the Moose pump.

 

[towcat]

I really dont think the tires or the fan should make a big difference. I am also curious as to to accuracy of your odometer.

they make a huge difference. i had a locked fan clutch on a 10hour freeway run and it killed my mileage. got fuel slips to prove it.
big tire are another issue too.

 

[Black dawg]

they make a huge difference. i had a locked fan clutch on a 10hour freeway run and it killed my mileage. got fuel slips to prove it.
big tire are another issue too.

at what rpm though? My locked fan shows less than .5mpg difference, but at 2k.

 

[towcat]

at what rpm though? My locked fan shows less than .5mpg difference, but at 2k.

3k rpm. roughly 85-90mph

 

[Devon Harley]

85-90 mph I would think the truck would use alot of fuel Wow I can't remember when I hit 85 last lol.

 

[BrandonMag]

Okay, I just got back from work and have read all of the replies.

To answer the most asked question: No, my speedo hasn't been recalibrated for the larger tires. If I've interpreted what I've read on here correctly, it sounds like my mileage will be off by about 10% because of this.

I know the locked fan eats up some fuel as well, I've run my truck w/o a fan and it's a noticeable difference. IIRC, I had my truck timed to about 7* BTDC @ 2K rpm a year ago.

It seems that if I bought a set of less-radical tires I would notice an improvement in mileage... what do you guys recommend for a good 35X12.50 street tire?

 

['94IDITurbo7.3]

smaller tire in physical size is the thing, not just getting a street tread pattern.

truck in my sig running 265-70-17's on the rear and 235's on the front i get 15 driving a "spirited" manner in the city. out of town out on the country roads i can get 20 driving how i want.

 

[tanman_2006]

Its gonna be hard to find a 'street tire' in 35". I would just look for a tight tread pattern and possibly ditch the body lift and go to 33's. I run Mickey Thompson ATZ 33x12.5 20's on my dmax, different animal that only runs 1500 rpm @ 62mph. The tire is heavy and aggressive but there is always a portion of each tread block on the ground at all times.

 

[02x72]

I get 16 with the 91 on the highway doing 75, roughly 14 city. Its in dire need of a fuel system upgrade, hoping that will get me a few more mpg's. Its 13-14 irregardless with the other one.