rest MPG

can any one tell me how to rest mpg average?

I assume you mean reset?
What year truck?
I'm not sure; but option package like LS or LT might matter...
My 2002 LS doesn't have the overhead display the LT has...

I have an '04 with steering wheel control buttons. When you have it showing in the display, you hold the arrow button on the right side to reset whatever's showing on the screen. Not sure if this will help with your case...