rpbfixit
SDD Junior Member
I need advice. i have hand calc. the mpg for the last 4 tanks of fuel in my 08 sdd 250 and my average is 8.7!! i fill up at the same shell station and do not drive like a race car driver. have a superchips cortex tuner installed and tuned to the mileage XS setting. Have'nt been towing and really making an effort to not let the turbo boost go past 10. fuel filter changed with last oil change (1800 mi. ago) does anyone have advice on what i should check? this can't be normal. i would actually pay someone for advice but i think I'm gonna have to get a second mortgage to pay for diesel. thanks