When filling the car always do the same thing. i.e. fill it until the pump cuts off OR fill it to the top of the neck.
I filled my wife's car & it shows poorer MPG as I fill to the top of the neck, she fills to first cut off.
Re LPG - some LPG pumps fill to a greater capacity than others, this can vary your MPG figure too.
by gareth111278 on February 24 2010
this tip works for 73% of voting Fuelly members.