Do Not Full Your Car Tank With Petrol

Do you know why?
Many of us are not aware that the petrol station pump has a return pipe line. When the petrol tank (in the 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 companies.