The gas volume changes by a factor of 0.001 1/K. That means, heating one liter by 20 Kelvin will expand the gas to 1,02 liter or 25 liters of gas to 25.5 liters. But the temperature of the gas pumped out of underground tanks is nearly the same all year and even heating the gas by about 20 °C in the summer never let the fuel tank leak, even when filling up to the lower edge of the tank opening.
The average fuel consumption shown by the board computer is so exact that I would realize a deviation of one liter on a full tank with ease. So there are some possibilities to check wheter the displayed information of the car or the gas station is wrong.
I would compare the fuel consumed, calculated from the distance and average fuel consumption of the last tank, with the displayed value of the gas station first. If this result would differ more than two liters or half a gallon, the displayed value of the gas station would be wrong in my opinion.
My maximum is ca. 8.7 gallons when filling the tank to the maximum and running over 100 kilometers on reserve.
One thing to notice: If the ground falls of to the right/front of the car, it is possible to tank 1 liter more than usual.
Mitsubishi Space Star 1.2:
Daihatsu Cuore L251:
__________________________________________
View my fuel log 2015 Space Star Klassik Kollektion+ 1.2 manual: 67.5 mpg (US) ... 28.7 km/L ... 3.5 L/100 km ... 81.0 mpg (Imp)