If a small child has ever asked you how petrol actually gets into the car – or if you’ve ever wondered yourself – here’s the answer.
Pick up the nozzle and the pump will select your fuel from the right underground tank. It also sends an electronic signal to the cashier, asking them to authorise the sale. The cashier will check that it’s safe to dispense fuel and you’re over 16.
A yes on both counts and the fuel is ready to flow. Pressing the lever on the handle opens a mechanical valve, letting the fuel into your tank. As you fill up, a meter measures how much is going in – until you finish, release the lever and shut off the valve. When the nozzle is put back on the pump, it sends a signal to the pump controller, safely switching off the electronics until the next customer.
Meanwhile, the details of your fuel are sent to the cashier, who puts it on the till ready for payment.
Ok, we’ll admit it’s not the most sparkling of dinner party chat. But a lot of work goes into making sure BP pumps are scrupulously fair and accurate.
Before a pump can be used, it’s checked, tested and granted a Certificate of Approval by the National Measurement Office. It’s then calibrated and sealed to stop any tampering.
As you use it to fill your car, the pump measures every drop it dispenses. However, the display can only show two decimal places, or 0.01 increments. This means the amount dispensed might be slightly higher than what’s shown.
For example, if you dispense just over one litre the pump will still show 1.00 litres, even though the true amount is, say, 1.005 litres. The display won’t change until you dispense enough to get to 1.01 litres, although the price you pay will always be accurate to the penny.
We can be sure of this because our pumps are remotely monitored every day and can be checked at any time by trading standards officers.