‘They Should Teach This in Drivers Ed:’ Woman Stops at Gas Station. Then She Reads the Fine Print on the Nozzles

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Stacy Fernandez

By: Stacy Fernandez

Jul 3, 2025 at 5:00am ET

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Topping up your car’s tank is tempting. Here’s why you need to avoid it.

People try to top off their gas tank for all kinds of reasons.

For some, there’s a satisfaction that comes with getting that even $40 pump or 10-gallon fill. Others are trying to optimize their trip to the gas station, thinking, “I’m already here, might as well fill it up as much as I can.” And others just don’t trust that the auto-shut off is detecting when the tank is actually full.

If this is a habit that you have at the gas station, here’s why it's time to cut it out.

Woman Shares PSA on Topping up Your Tank

In a viral video with nearly half a million views, content creator and blue-collar worker @thatgirlpilotcar shared a rule you should be following at the gas station.

She pointed out that the fueling nozzle specifically states in writing (bet you never noticed that), “Do not top off.”

She pointed out that there’s a charcoal filter in the fuel filler neck, and every time you try to squeeze more gas in there, it backs up into that and turns the filter into a “non-breathing solid lump of charcoal, and then you will have hell filling up your gas tank.”

“It’ll kick off constantly ‘cause it’ll wanna back up, spit back at you, and you’re gonna have to spend some money to have somebody replace that little breather,” she said.

@thatgirlpilotcar said she was speaking from experience, given that her mom “was the worst about squeezing every drop in there that she could,” plus she herself had a van that took 15 minutes to fill up because of this issue.

She finally got it fixed, but it set her back several hundred dollars.

What Happens When You Top Off Your Tank?

The TikToker is right: Topping off your car could damage the onboard refueling vapor recovery system (the charcoal bit she referred to). The charcoal canister catches harmful fuel vapor and reabsorbs it with activated carbon, reducing hydrocarbon emissions by about 95% during the refueling process, Consumer Reports explained.

Adding too much fuel can saturate the charcoal canister, damaging it and rendering it incapable of properly catching the harmful vapors.

While this system usually lasts the lifetime of a car, topping off could lead to an avoidable and expensive repair.

When you top off, gas can also spill on the ground, which is a safety and environmental hazard.

On top of that (no pun intended), modern nozzles are designed not to overfuel your car, so if you squeeze extra, the price on the screen goes up, but more gas might not actually go into your car, instead reversing back into the pump, KwikKar pointed out.

“Topping off your car is dangerous to you and your car, and may cause problems. Your best bet is to stop pumping when the fuel pump clicks off,” the article read.