
Originally Posted by
niky
There's a big problem with calculating based on so little gasoline... different pumps shut off automatically at different fuel levels, and air bubbles can spoil your calculations.
One team at a Honda Challenge protested because the gas boy overfilled their car by a bit on the refill, ruining any useful calculations you could make from the short 40 km course.
You should fill up, wait till the tank is almost empty, and fill up again at the same pump. There's no guarantee that your odometer will read correctly or that you will get the same amount of gas, but this method lessens your error to maybe 5% or less.