Hi i have a 00 f350 ex cab longbed 6 speed 6 inch lift 36 inch tireds 4 inch exhaust turbo back 6637 filter hutch intank mod shimmed fpr and a predator programmer. truck has 271000 miles on it has used 2 quarts of oil in 6k miles and i can atribute some of that to changing 3 injectors. When it was stock i got 13 mpg pulling my gooseneck with a f150 on it thru the mountains. I realy havent paid much attension to mileage as i had a car to drive but the trans went out of it and now i drive the super duty every day. Im only getting 11-12 mpg now i bty no means abuse it but i dont drive like grandma either. Could that tuner be causing that milage? a dp is next inline but $ is tight and 120 a week in diesel dont help. I was thinking i got 18 mpg empty stock I expect a smal drop with the tires last time i pulled the goose neck i got 9mpg any ideas
thanks

 

Those tires and lift are probably a mojority of the issue to be honest, but there are a few things I would check to be sure. First is the air cleaner, make sure it isn't too dirty. I assume you have looked at it though seeing as how you have a 6637.

The next thing would be to check that all your intercooler boots are tight.

The final thing is to get under the truck and look at the up -pipes. See if there are any soot markings at the junction with the exhaust. I bet there is. You will lose a bit of mileage there for sure.

 

my rules of thumb: each inch of lift gives you 5% Less mileage (average) on the highway and it is cumulative. wider aggressive tires do the same, but I don't have a formula. Fuel has gotten so full of chemicals that it really isn't fuel any more.

Some people swear by the tuners giving them more mileage, and they will do so at the expense of driveability. The problem is that tuners tend to force the right foot further into the floor so it is hard to realize any gains.

Finally: drive it like a grandpa over 90, never go past 2000 rpm, and realize that every time you mash the go pedal, you just lost 1 mpg. Most poor fuel concerns are caused by the loose nut attached to the steering column.

I claim 20 to 25 in my bone stock 2000 depending on my style and trip type. but It is my $.02 and your mileage can and will vary.

 

This is so true and so damn funny!!!!!!!

 

four common things could make you loose MPG besides the tire,lift and a heavy foot...low grade fuel, boost leaks,up pipe leaks and a pluged EBPS tube...

Welcome to guzzle's Exhaust Backpressure Sensor Cleaning Maintenance Web Page

 

I just cleaned the ebps tube 4 months ago the 6637 isnt new anymore but far from dirty
theres no apparent boost leaks i built 21 psi easily all boots are tight and not torn as i had them off when i pulled valve covers not too long ago. I shift around 2200 and run 60mph on the 6 miles i drive highway to work keep in mind speedometer hasnr been recalibrated.

 

You can add ten percent to your mileage simply because the speedo is reading slow. Check your odometer as you drive through a measured mile marker. If you show 9/10 then you know you are recording 10% slow. Watch the radar picture takers also in the comedian strip! If you changed your gears to get back to the same cruising RPM's as the peanut tires it would help your mileage. Remember the big meats drag more friction she said.