total mileage less the volume of diesel you pumped. eg. 300km divided by 30L = 10 km per liter.
for taxi, this calculation may not 100% accurate becos of waiting and queuing time at the AP.
so it depends if the driver Q and wait most of the time or chiong most of the time.
thank you taxiuncle for the tip! shall try it out he next time i fill up! usually sonata fc is usually about 9km/litre? mine is left about 1 yr (veh registered in 2008)