Originally Posted by Don121
I am using 87 octane fuel and 35" fierce attitude M/T tires. I mean I know switching gears and going to a A/T tire will help but this seems pretty low even for how mine is set up..
I do agree it does seem low. I'm getting about 13-14 when I drive through DC, I have a stock set up still, but I have a hard time believing yours would be that much worse.
You may want to try a thorough cleaning. Here's a link to another thread....granted his truck is a different gen but I'm thinking your problem sounds similar. He replaced his O2 sensors and re-calibrated his odometer for his larger tires.