(Dons appropriate clothing, this time itÃ¢â‚¬â„¢s an anorak with the zip pulled right up and all the poppers fastened).
Checking my spreadsheet I see that my personal best was 669 miles on a single tank full. This took 45.25 litres to refill (so close to 10 gallons we wonÃ¢â‚¬â„¢t argue). Giving 66.9 MPG and a Cheshire cat style grin.
(Removes anorak and puts it back in cupboard with pedants hat).
It is common to find that the onboard computer will differ from MPG calcuated manually (Miles travelled / fuel to refill the tank) both systems have good and bad points. Long avarages taken between known 'fulls' are probably the best real life indicator but I do like a good headline figure in the 60's.
Reaches for anorak again. Range is ultimately governed by how far you dare to go after the last blob on the gauge starts to flash, there is a figure somewhere on the Pruis forum for how much fuel remains but I generally go up to 50 miles.