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MOST drivers fill their cars with gas and don’t think about how their fuel pump automatically shuts off.

But a fascinating design helps gas pumps achieve this convenient automated response.

Gas pump mechanics are mechanical and more straightforward than you may imagineCredit: YouTube/Steve Mould

A gas pump’s operation is entirely mechanical.

When you pull on a gas pump’s handle, a lever opens a valve within the handle allowing fuel to flow into and through a thin tube to your tank.

The end of this tube is open, which causes air to move back into the gas pump during a refill, Steve Mould reports.

Once your gas tank is filled, the tube starts sucking in gas instead of air.

Since fuel is more challenging for this tube to inhale, a chamber within the gas pump feels a wave of negative pressure.

This negative pressure is designed to reverse all the pump’s previous movements, causing the valve to close and stop gas flow.

The scientific phrase describing a gas pump’s automated response is the Venturi effect, Science ABC reports.

The Venturi effect happens when the thickness of fluid exceeds the density of air.

One viewer of Steve Mould’s YouTube video commented: “I tell you, if my professors had been as dedicated to explaining the venturi effect as you did in this video, I’d probably have picked up on a significant amount of the things they were teaching me.

“A lot of how aircraft work is based around the venturi effect and the bernoulli principle because the one thing aircraft have in abundance, is air moving rapidly in a single direction lol.”

A gas pump’s automatic shut-off response ultimately helps prevent a driver from spilling fuel from their tank onto the ground.

Gas outside a car’s tank or pump is a serious fire hazard — especially at a fuel station.

Steve Mould describing what actions a gas pump takes when it begins sucking in fuel instead of airCredit: YouTube/Steve Mould