Measure Capacity of your Car Fuel Tank

Many of us are not aware that the petrol pump has a return pipe-line. When the petrol tank of your car reaches full level, there is a mechanism to trigger off the pump latch and at the same time a return-valve is opened at the top of the pump station to allow excess petrol to flow back into the sump. But the return petrol has already pass through the meter, meaning you are donating the petrol back to Petrol Pumps.