I have a 2009 F250 diesel, my mileage is terrible. I am only getting about 11 to 12 miles per gallon, I was told I should be getting around 18 to 20.
I need help with this problem!

 

i have a 2008 6.4 & i only get 12 to 14 mpg

 

Delete egr and dpf and youll see high teens and your rear pistons wont burn up

 

Deleting the DPF and EGR will increase your MPGs, but 18-20 MPGs isn't going to be easy to achieve.

I can get 17 MPGs (empty / un-loaded) if I keep the boost under 10 PSI and putt-putt drive. All of my miles are HWY miles with a 3.73 rear-end, 2WD drivetrain, and speed kept at 60 MPH. That's running the Spartan 300 tune (supposedly one of the better MPG tunes). I also get my fuel from a very well-known place in town that has good quality Diesel and I run additional Cetane Booster on top of that to increase the Cetane even further.

Don't ever go by the little computer on the dash that "calculates" your MPGs. Though it can be useful if you reset it while cruising down the HWY to see "approximately" what your MPGs are for that little stint, it goes full-retard in the grand scheme of things after a bit of City / HWY driving.

A little more information on your truck will help us approximate what your MPGs should be (give or take). DPF / EGR delete? Which tuner is being utilized? Rear-end gear ratio? Tire size? 2WD / 4WD? Hubs locked? Cab configuration? Etc.

Hope this helps in some way.

Cheers!