Quote Originally Posted by macropod View Post
If you're working off the fuel guage, the results are essentially meaningless. Unless you completely fill the tank each time and note both how much fuel the bowser (or trip computer) says was used and how far you went, you'll never get accurate results. having said that, though, I've encountered some pretty inaccurate fuel bowsers, too.
When my fuel gauge died I only ever filled my tank to the absolute brim when I filled up, then reset my fuel stats before I left the station and ran off the fuel total amount and k's travelled. That is by far the most accurate way to determine your mileage I've found.