My 2008 f150 lariat has a fuel mileage read out on the dash how accurate is it? Do I have to reset it each time I park it then drive it? Never had this on any of my f 150's

 

Test it over several tanks by manually calculating your mileage and comparing it to the dash read out.

The accuracy of the fuel economy reading in the truck will vary based on driving habits, health of the drivetrain, modifications, and various other factors. As a result some gauges will read close, others can be really inaccurate.

 

I like to reset mine after each tank. I find the average to be pretty close. Sometimes its within .2-.3 I used to never use it but now I use it each tank and check it against my Fuelly app that I use. If you never use it then it becomes a cumulative average which I really don't care about.