Why You Shouldn’t “Top Off” Your Gas

ACA explains the harmful effects of topping off your gas

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It’s something we all do: You’re at the gas station, you set the gas pump at automatic, you let it fill up the car until it’s done, and then you squirt in a little bit more. It’s a common enough practice, “topping off,” but like your mother used to say, “If everyone jumped off a bridge, would you do it too?”

You certainly wouldn’t jump off a bridge. That’s just common sense. But believe it or not, you shouldn’t be topping off your gas either! This is a bad and potentially expensive habit that you need to break. Here’s why:

A gas pump has something called a “vapor recovery system” that actually sucks excess gas back into its system. So guess what? That extra bit of gas you think you’re squirting into your fuel tank? You’re actually emptying it of the gas you just paid for.

If you do top off and the vapor recovery system has sucked in some excess gas, the next time someone uses that pump, it has a chance of breaking. If it doesn’t break, the extra gas will be dumped into their vehicle and cause it to overflow.

If you pump your own gas, you know what gasoline smells like. It’s strong. Because of the vapors that gasoline produces, your gas tank needs extra room for it to expand. If you manage to get more gas in the tank then there should be, it can back up into your car’s vapor collection system. This causes a bunch of headaches: it can collect in your vapor pressure port and contaminate the outer tank; it can force fuel through the vents of the filler neck or cut-off valve; and it can collect in the fuel lines.

Speaking of headaches, if your gasoline is collecting in the lines or flowing into other parts of your car, you’re going to smell it. And then it’s not just going to be your head that hurts, it’s going to be your wallet.