as a rule of thumb, add about 5-10% of the tanks stated capacity onto the true capacity of the tank. when the display reads 'empty' and the engine cuts out, your fuel tank will never be empty. what happens in that instance is a fail safe mode is activated which shuts down your fuel pump to stomp it pumping air which is detrimental to the tank and pump. there needs to be that extra 5-10% to allow for EVAP (fuel vapours)