There are several things that could cause low mpgs. The bigger tires and lift will kill the aerodynamics and increase the rolling mass to get your truck rolling and keep it up to speed. Also, don't drive it in 4wd..

Check for a brake caliper that is dragging. Someone on here just had a problem with his brakes that were dragging and gave him awful braking and horrible mileage.

 

If you have 37 inch tires without correcting the speedometer/odometer, your math will be off 15-18%

 

my 2004 with 35s got average 13-15mpg... you need to convert your odometer reading. You are probably seeing 12 mpg I'll bet.

Also the 6.0 wont get much more mpg at all with light driving, just drive it normally. When you got it, did you change both fuel filters, and oil at least?

 

Also the 6.0 wont get much more mpg at all with light driving, just drive it normally. When you got it, did you change both fuel filters, and oil at least?

I'm getting 20 mpg in my F350 but only if I keep RPMs at or below 2000, which is about 64 mph. Custom tune from Wildman for fuel mileage helps.

 

Thanks for the replies, yes the timing cover job did oil change. Not due for another 4-5k. And yeah even if I 12% off I am at most getting 10Mpg, I drive 60-70mph on freeway. I am doing more
City but it is not good mpg. I took in mind the wheel radius.

 

To be honest I am not 100% sure how to turn on the 4wd is it just that switch? I heard something about turning wheels. How can I calibrate the mpg , is that something I can do or shop
Has to do? My dad has a 7.3 he says he gets 15 all day.

 

Well are they 35's or 37's...? kind of matters quite a but...better what exact size are they...not just dia. There can be quite a bit of diameter difference even among just a 35" tire depending on dimensions. Better yet actually measure the tire overall circumference. You can get the revs per mile from the manufacturers specs or use a tire calculate like this one below but measuring is even better but the calculator gets you close enough.

Just click on the tab tire size calculator..punch in your actual tire size and note the revs per mile. Then punch in the stock size that came with it..should be on the drivers door pillar I think. If you are running 37's uncorrected you might be way way off depending.
https://tiresize.com/calculator/

Your last fill up was what..9.1 MPG or so. If you are running big ole tires and the computer is not corrected your calculated MPG will suck. Assuming that is so....you probably are getting closer to 11-12. For city driving mostly with big damn tires I don't see a huge issue...assuming an uncorrected Rev per mile.

You really need to know exactly what size tires you have not just they are 35 or 37's.

So bigger than stock tires..a big ole lift..an uncorrected speedo and odometer...your probably about right. Also how wide are they..are they big old mud swampers or narrow highway tires..usually don't see guys puting a narrow 35 or 37 on. So..wider the tire the less the MPG due to simple increased friction to the road via a larger contact area. Won't kill the MPG by a huge amount but start adding up uncorrected odometer..big wide tires with a larger diameter and a big lift and it adds up quickly.

Your Dad has a 7.3..but how different in setup...? So might not be fair to compare?


Now..I was able to correct mine with an SCT tuner. Some people say they have not been able to so I can't promise you will. It can be corrected in a tune but then you need a tuner like an SCT anyway first so.....?

Can try the Ford dealer first and ask them. Oddly I have heard conflicting answers on that but I have no first hand knowledge.

Last..do you have a GPS or smart phone...or do you know where this a measured mile on the highway. I grew up near the Grapevine in SoCal and know there are ones along Ca. highways.

Either find a measured mile and set your trip Odo to 0 and try and go 10 miles if possible and see what the split is from the two....bet your off by a half mile.

Or use your GPS for speed and hold it on a straight highway for a few miles. Set the cruise and see what the split is between the GPS and speedo speed. Either of these methods will give a rough % of or if your comp has been corrected for revs per mile and if not how much off.

But I would not start chasing other issues first until you know this info and correct for it...either with a computer flash or tuner..or just mentally. Don't start chasing what iffs until you know your data is accurate and never assume the PO knew what he was doing.

I think if you are averaging 12 MPG in mostly city with big ole tires and a lift...then you are about right.

If you were all stock...and driving mostly highway with some city then you should get at least 15 but would think 16-17 would be reasonable mostly highway at 65 MPH.

As a note.. I have an F350 dually... slightly larger than stock tires and 4.3 gearing. I get 12-13 mixed and about 15.5 mostly highway at 60-65 unloaded. Hand calculated with corrected odometer. Best all highway MPG at 60-65 was 16.8 MPG.

 

You have hubs in the center caps of your rims, sometimes those stick in the locked position, or free position. You have to spin the shafts to know for sure if they are free. And those being locked all the time could have an affect on your fuel economy for sure.

 

Check your tire pressure, put less aggressive tires on it, regear if you have 3.73, etc.

 

I have 37 13.50 20s on my 6.0 and getting around 17 on just highway and averaging 15mpg all around unloaded. Running tunes. If I take the tunes off I lose 3-4 mpg

 

For stop and go traffic in the city, I'm stock and I get 10 MPG. On the highway, its 15. If it's a cross between stop and go and highway I'll get 13. I had Mud Tires on mine before, and that dropped highway to 12 to 13. I have All Terrains now. Best mileage for me is at around 180 ECT, 195 EOT. Colder or warmer than that, it goes down by a couple of MPH. I now have a BPD cooler.

If the 9 MPG is stop and go with your lift and tires, I think that could be correct.

For me gas mileage is the least expensive thing in the truck, the rest of the maintenance is what jacks the price per mile up.

 

My 03 250 crew cab is rolling on 35s and 6in of lift. With an SCT x4 using the street tune I'll see 19-22 on the highway all day long. City is more in the area of 12-14. Not sure what your issue could be. Tuning could be jacked up or its a legit mechanical issue.


2003 F-250 Crew Cab 6.0L. SCT X4,S&B intake, 5" turbo back exhaust, running 35x12.50s and 6" of lift

 

My 03 250 crew cab is rolling on 35s and 6in of lift. With an SCT x4 using the street tune I'll see 19-22 on the highway all day long. City is more in the area of 12-14. Not sure what your issue could be. Tuning could be jacked up or its a legit mechanical issue.

I'm seeing the same thing. 20-23 on full fuel tune on the Livewire. City is 14-16. Of course that's driving like a normal. One push of the pedal and its like 6mpg. 6in lift, 37 toyos.

 

I went to smaller tires and I saw a huge increase in mpg, tires kill it, not only size but tread, went from 35s that were open country mud terrain, so the nitto g2s which are street tread. I can get almost 500 miles too a tank now.

Youre lift and tires are killing you. My odometer said 463miles, google maps said 493. Im still bigger than stock tires so im getting more miles than recorded but not a lot

 

Your attention to MPGs are killing you.

Fixed... enjoy the truck and quit counting beans.

 

I will comment again because part of my post was used. Seems like a lot of negativity on this forum or something, crazy lol. Thought it was to help each other, anyway. 3 ppl are saying their getting 19-22. I know for a fact that it's possible and being done on "6in lift running 37x22x13.50 Toyo". What Clay said about taking off and staying below the 2000rpm range is absolutely correct, but you have to stay diligent, which obviously the "nay sayers" aren't. Tuned staying out of the pedal on the interstate I'm getting 19-22mpg, flat road cruising. That's "Hand Calculated" "Highway Mileage". The numbers are achievable.

 

First off, I don't want to be negative. Sorry for the negative sounding post. I agree that sometimes this forum seems to have that quite often.

Next I'll reply

True, but when people say they can get 19-22 "All day long" makes it seem like you get it no matter what, when in reality there are very specific conditions that you get to do that. Same speed, flat grade, no speed changes, no stops, etc. Heck, I could probably get 25 if I was going downhill for 300 miles at 55 mph with a tail wind, but that doesn't happen on this here Planet Earth. I am not being a Nay Sayer, I am being a realist so people don't read posts like that saying you can get 19-22 all day long and expect that when they go buy a 8000 lb truck and throw on a 6 inch lift with 37 inch mud tires. It doesn't happen in normal, day to day driving conditions, at least in my area. There are hills, stop signs, speed changes, etc.

By the way, I am tuned, have stock Michilin AT tires and believe me don't drive my truck hard. Best I have gotten was 18.2. With my 7.3 best I got was 23 (on a 15 mile trip..ha) I want it to last and don't want HG issues.

 

You don't even know if your tires are 35 or 37s? Sorry I quit reading after that, may have found some flaws in your equations.

 

Don't be so sensitive, it's all about driving style and conditions.

Hence why the "I get 6" was quoted.

 

All good Heavy_GD

 

Wasn't actually referring to your comment and I'm not the one who said "all day long" . Not trying to get into a pissing contest either My point was....that the numbers are achievable. I get 19-22 period. I live on the East Coast at the ocean. 25-30 miles west of here its hilly and rolly. Those are the numbers. They do have variation but that's been my typical experience. Not all trucks are built the same, driven the same nor set-up the same. But for ppl to say that it's impossible are wrong. And if ppl read posts like this then they need to "read" the post and come away with knowledge. It's obvious that I stated my truck wasn't stock and was running a tune. So at that point light bulb #1 should have gone off. The other fella stated that he was running a custom street tune. Light bulb #2 should have went off. I mean it's common sense. If your in the hills your mileage is going to suck regardless of what you drive, again common sense. To say that the #'s "can't" be achieved or someone is lying (<<again, Not quoting you) is non-sense. Just because you aren't doesn't mean you can't. I'm done.
Oh and btw.........25 mpg going 55 downhill for 300 miles sucks. Should be alot better than that lol
Thanks for the help I've gotten on here. Hagd Bierman

 

Here is some actual data for you. Mods in sig and garage (except for Stage 2 turbo, have had that less than a week). Best fuel mileage was 19.44 mpg. I typically get the same or worse fuel mileage on the highway with 4.10's at ~2000 rpms = 62 - 63 mph. Sucks during the winter months (winter fuel, cold weather, warmup).

 

I really wish you hadn't posted that. It made me go look at my Fuelly stats where I saw I've spent almost $10.5k on fuel in the last 55k miles. :doh:

You can see by my banner that I'm averaging 16.5 mpg over that 55k, but it's a bit deceiving because for the last year or so I'm actually averaging closer to 15. Still trying to figure out why I lost 2-3 mpg. I was right at 18 mpg for quite a while. The change coincided with my turbo replacement to a KC 1.5, so I'm assuming leak, but haven't found it yet.

 

I am running 33's 4" lift 373 gearing currently getting 16 17 tuned for the stage 2 turbo.

the kicker is not tuned for the stage 2 i hit mid 20's but it is smokey which is unacceptable especially in the peoples republik of kommiefornia :doh:

i think the trans tuning and shift points play into that to a large degree.

I want to milk the best mileage i can out of it but i need it to clean up in the process.

that is my goal get back into the 20's running clean even on slight uphills which living in the mountains there are a lot of :nod:

 

Here are my results. 2005 CCSB 4x4. This has a lot of in town and towing 8k camper). SCT tuner on tow turn. Average driving (get on it every so often).

 

Here are my results. 2005 CCSB 4x4. This has a lot of in town and towing 8k camper). SCT tuner on tow turn. Average driving (get on it every so often).

View attachment 521842

What app is that? I have been using fully since 2011 on my two trucks.

 

Above all else a good brake service is always in order for these trucks... More often than not crappy fuel economy is caused by 2 things. First and foremost its a 9000lb diesel pickup... Second, 1 or more dragging calipers.

But fuel plays a big part as well, if you live in the north and deal with winter fuel you will see a huge loss in mpg (and a noticeable power loss) during the winter. Also if you are driving a lot without the motor completely up to temp then again, she isn't going to burn the fuel efficiently and you are going to be filling up a lot more.

Finally, yes you really do need to find out exactly what size tire you have and account for that. You could also have some injector issues... But start by telling the truck what size shoes she is wearing so the odo is accurate.

 

Above all else a good brake service is always in order for these trucks... More often than not crappy fuel economy is caused by 2 things. First and foremost its a 9000lb diesel pickup... Second, 1 or more dragging calipers.

Hmm, that actually goes for ALL vehicles with disc brakes. However, these trucks are not more prone to a stuck caliper anymore than a Prius.
Simply grease the caliper slides every 4th time you rotate your tires or every so often (whatever feels good) and you wont ever see that problem. Also a must do is to change out the brake fluid every 100k or so miles and NEVER use a can of fluid that has been opened. That fluid is hydroscopic and draws moisture. Moisture that will wreak havoc on a braking system if left to do so.

 

Yeah i am new. I barely got the truck that is why i am unaware of what mods it has. As i said it has a turbo whistle and a lift. My friend has an 03 f250 lifted 10 inches he says he gets 350miles on 25 gallons. I usually keep it under 2000 rpm, but maybe something is dragging(brake) it is really slow, i know its a truck but might have to look that up. My friend didnt have to modify his mile reader or anything, so something is off here. I posted a picture of the truck so you guys can guess/estimate the lift. The tires are 315/75/16. i just recently got 205 miles on 22 gal. But when i fill it up again i will track my miles with my iphone navi.

Do i have to make a new forum if i want to know a question about o2 sensor not being ready? my smog test failed because a monitor isnt ready?

 

For MPGs that bed cover makes them worse (look up the mythbusters test).

The 6.0 doesn't have any o2 sensors to my knowledge, so I'm guessing the EGR isn't ready and may be deleted/disabled.

 

I change my fluid every 2 years, if I went 100k miles it would be 5-6 years before it got changed.

 

Going off the reported stock tire size verses what you have now you have increased circumference by just under 10%.

If you keep it at a steady 60 MPH your GPS should say 65-66 if you are on a fairly straight road..GPS doesn't get curves.

This should also mean your odometer is off about 9.6 miles per 100.

SO even with this corrected your mileage still sucks..just not suck as bad...but how do you quantify levels of suck.

Stock tires have a Rev per mile of around 638 the ones you have now are 583. Thats just going by a tire calculator but actual varies among brands and tread but will be fairly close. The manufacturer will have the exact number on the tire description...but like I said this is close.