A YouTube animation reveals the clever mechanism behind fuel pumps.

While filling up your car, you're probably more concerned about the cost than pondering why fuel pumps automatically stop.

Thanks to YouTube, a detailed simulation shows exactly how gas pumps know when to stop dispensing.

ZackDFilms has built a reputation on YouTube for educational content that usually covers some pretty grim scenarios.

He's explained why you shouldn't pop blisters, what happens in your lungs when you smoke a cigarette, and (less grim) even created guides that could potentially help criminals crack safes.

This time, he's kept the grossness and fear factor minimal in his video about fuel pumps.

Filling up may seem straight-forward, lift the nozzle, press some buttons and swipe your card. However, what happens inside the fuel dispenser is a bit more complex.

"When you pump gas in your car, there's this tiny hole connected to a valve that sucks in air," Zack explained. "This air intake keeps the fuel flowing smoothly as it fills your car."

When the tank fills up, Zack noted that this hole becomes 'covered,' stopping airflow and creating a vacuum inside.

Although the bottom of the pipe remains open, 'this change in pressure triggers the pump to stop the flow of gas.'

This component you also might know as a check valve.

According to HowStuffWorks: "Using a check valve to hold the gas inside the pipe prevents unnecessary wear and tear on the suction pump and assures that a supply of gas will remain in the pipe so that the next customer won't have to wait for it to be drawn all the way up from the tank."

Viewers in the YouTube comments have been thanking the content creator for helping them learn stuff in an easy way.

"Finally, parents can answer all of the questions from the children. This channel is a blessing," a YouTube user commented.

"Whoever invented this was a freaking genius," a second user wrote.

"Ah this will help when i can afford to completely fill my tank," another YouTube user wrote.

"Never thought about this ever before but this makes perfect sense," a fourth viewer admitted.

Similarly, the flow meter follows a similar mechanism.

As petrol travels upward into the dispenser, it passes through a flow control valve that regulates the fuel's flow rate. This works via a plastic diaphragm that compresses more tightly into the pipe as fuel flow increases, consistently leaving just enough space for the correct amount of petrol to pass through. If you've set a predetermined fuel amount, the flow slows as you approach your limit.

The more you know!