lost my fuel mileage need help

[dixiedevil]

I have a 2000 Ford F-250 4x4 offroad that i have lost fuel mileage with for no reason that i can tell, i always hand calculate my mileage btw i was getting 20/21 mpg now its more like 13/15

truck is the same way its all ways been this is what i have done so far
got new rancho rs5000 shocks
replaced all uni joints
trans has been flushed and new fluid
tires have correct air pressure
front end aligned
new fuel filter at bowl (not sure if tank has a filter)
new icp sensor
new back pressure sensor (tube was clean)

truck still runs just as good as it ever has so i'm lost, i will list add on under this but keep in mind i had all add ons before fuel mileage went down

leveling kit
35/12.50/17 tires
edge attitude 2nd level or 80hp mode

i do notice that if i use 30 ozs of diesel kleen (gray bottle) i pick up about 3 to 5 miles where before i used 15 to 20 ozs

like i said this makes no sense to me at all, I was told that the diesel you get now is different than diesel we got a year ago

the only thing different i can think of is i had to get a new icp sensor because my other one crapped out and made engine chug but i cannot remember if this was before or after fuel mileage went down.

any help is good help thanks in advance

[dixiedevil]

just bumping my post

[Indy]

How many tanks of fuel has this been happening?

[dixiedevil]

Originally Posted by Indy

How many tanks of fuel has this been happening?

at least 50

[Codum]

With 35" tires 13-15 mpg would be correct. If you were getting 20-21 something was wrong. When you were calculating the MPG at 20-21, was that based on 1 fill up or 10 fill ups? The best way to know you MPG is by using fuelly.com (see my signature below). If you have a smart phone it easy to do every time you fill up. I have heard plenty people claim 20-21. Go to fuelly.com and look at all the 7.3 trucks. You can do a search by any vehicle year and fuel type. No 7.3's on there are getting 20-21. May be a few 18 mpg trucks but they are 2wd speed limit only highway trucks with a manual transmission. Not wanting to knock your claim, but think you may have made an error on your calculation or fill up procedures when you got the 20-21 mpg as its not going to happen.

[dixiedevil]

Originally Posted by Codum

With 35" tires 13-15 mpg would be correct. If you were getting 20-21 something was wrong. When you were calculating the MPG at 20-21, was that based on 1 fill up or 10 fill ups? The best way to know you MPG is by using fuelly.com (see my signature below). If you have a smart phone it easy to do every time you fill up. I have heard plenty people claim 20-21. Go to fuelly.com and look at all the 7.3 trucks. You can do a search by any vehicle year and fuel type. No 7.3's on there are getting 20-21. May be a few 18 mpg trucks but they are 2wd speed limit only highway trucks with a manual transmission. Not wanting to knock your claim, but think you may have made an error on your calculation or fill up procedures when you got the 20-21 mpg as its not going to happen.

this is how i have always checked my fuel mileage i reset my trip then when i go to fuel up i take my miles on the trip then divide them by how many gallons of fuel it took to fuel up so if i had 330 miles on the trip and my fuel up was 21.965 gallons my fuel mileage would be 15.023902 i just round to nearest number which would be 15 mpg

also this was going by numerous fillups so more than 10 fill ups

my truck is auto tranny but i also use the dynatrac free spin system so no front axle drag

my truck when i first got it had over 200,000 miles and i was getting 412 miles to the tank and normal fuel up was 21 gallons which is 19 and a half mpg

that was normal for me from may 2011 till feb 2012 then went to 380 miles for about a month then 300 miles thats when i started using 30oz's of diesel kleen instead of 16oz's which brought me back up to 375 now i can put 40oz's or even 60oz's and i still get 300 max

as far as no 7.3 can get 21 diesel power mag or it may have been 8 lug back in 2008 maybe 2009 proved that a 7.3 using syn oil,aftermarket cool air intake,dyna trac free spin and a few more add ons could get up to 23mpg as a daily driver
so there are ways to achive 20+mpg with a 7.3 turbo 99 and newer

my other F-250 aways got 18mpg but only after i installed a dyna trac free spin on it before the free spin i was getting 15 to 16mpg

I did notice when i was in illinois back in march that running there bio diesel mix made my fuel mileage drop to about 10 to 12 mpg when i got home i changed the fuel filter thinking this would help i also noticed that since then my fuel mileage has been not so great, i have ran bio diesel before and gotten great fuel mileage but this could be different because of the precentage of bio mix i think before when i ran bio no problem it was a 15% mix where this last time it was a 40% mix.

I dont think its the bio its self to blame however i do think this has something to do with 1 or more sensors that may be failing but arent throwing codes yet as the only sensors i have replaced so far have been the ICP and back pressure i also cleaned tube leadign to back pressure sensor as i was told this could also cause a problem.

If somethign was wrong with the truck i was unaware as it ran as good as it ever has even when pulling a 30ft travel trailer so i'm at a loss if it was something going wrong as far as i can tell it never hurt the truck so i wish it would break again lol

[Codum]

Ok, 21 may be achievable with various add ons and the right driving conditions, but the percentage of trucks/drivers who achieve that are very very low. I do hope you can educate me on one thing, the spin free system, how is it different than the stock system as it relates to spin free. I know it's stronger, cheaper to replace bearings, but how does it spin free er than the stock unit that is also a free spinning unit. Just curious how it helps your mileage since the stock unit is a free spin unit too?

[Joel]

I bet your up pipes are leaking.

[dixiedevil]

Stock hubs arent free spin even when you unlock the hubs your front axle still turns because of the vacuum lock system, with the dyna trac free spin system you no longer have the vacuum lock just manual so when your rolling the front axle does not move until you get out and lock the hub in and of course the added strength since the bearings are spaced apart and to change bearings cost $40 per side

[Codum]

The vacuum system on the stock unit only locks the hub when you turn the dial on the dash to engage the transfer case. You may have seen an increase in fuel economy due to the lower rolling resistance inherent to the Dynatrac design.