ELI5: Why does driving just a little faster use significantly more fuel?

Driving just a little faster uses significantly more fuel because the air pushing against your car fights back much harder the faster you go.

Imagine running through a swimming pool. If you walk slowly, the water gently moves around you. But if you try to sprint, the water suddenly feels like a heavy wall pushing against your chest, making you sweat and breathe hard after just a few steps.

When you drive, your car is doing the exact same thing, but in an ocean of air.

• The Invisible Wall: Air might seem light and empty, but when a heavy car smashes into it at highway speeds, that air pushes back. This push is called wind resistance or aerodynamic drag.
• The "Square" Rule: The sneaky secret of wind resistance is that it doesn't grow at a normal, steady pace. When you double your speed, the air doesn't just push back twice as hard—it pushes back four times as hard.
• The Extra Effort: Going from 50 to 60 miles per hour adds a little bit of resistance, but going from 70 to 80 miles per hour creates a massive amount of extra drag.

So, even though driving 80 miles per hour only feels a tiny bit faster than driving 65 miles per hour to you inside the quiet cabin, your engine is working almost twice as hard to push all that heavy air out of the way.