We’ve all done it before. Well, in my case before I was yelled at by my dad, that is. – “topping off” your gas tank at the gas station. I’ll admit – I used to do this a lot. But, not anymore: According to my dad and many other car experts, this is a big “no no,” and could lead to expensive problems with your car! I just thought I was getting my money’s worth out of each gas stop.

“By topping your fuel tank off, it can either overwhelm your evaporative system and break something or cause a hazardous leak by the excess pressure in the system,” says Ed Nemphos, owner of Brentwood Automotive in Baltimore, who adds that gas needs extra room to expand in the tank. Now, these were a lot of words that, frankly, I needed my dad to put into English for me. But in essence, topping off your gas tank can cause pressure to build in the tank and flood the carbon filter vapor collection system, only meant for vapor. As a result, the overflow can affect your car’s performance and could possibly damage the engine.

Overfilling the tank can also shorten the life of the carbon filter canisters. Those canisters can cost anywhere from $200 to $1,500 — not to mention the cost of an entire engine! You know that we love to see you here at Younger Mitsubishi, and we’ll be happy to help you out,  but we’d prefer to see you under happier circumstances. This isn’t something I’d want to mess around with for the sake of squeezing a few more drops of gas into that tank.

“According to the EPA, once a gas tank is full, there is no way to fit any more gas in the tank. Gas stations are equipped with a vapor recovery system so that if a tank is full, the pump will pull the extra gas you’re trying to pump into your car back into the station’s tanks. This is a safety precaution to ensure excess vapors will not escape into the environment.” What this means for you, is that you are then paying money to “top off” your gas tank, BUT you aren’t even getting the gas that you paid for. At that point you’re just throwing money at the gas station, totally wasting it.

In addition, topping off the tank can result in a greater chance that gas is spilled onto the ground, and these gasoline spills can contribute to bad ozone days as determined by the Air Quality Index. If you thought a bad hair day was rough, let me tell you, bad ozone days are SIGNIFICANTLY worse. Another factor to consider is that if you happen to damage your car’s vapor recovery system by topping off your tank, it also won’t be able to protect people and the environment from harmful vapors caused by improperly processed gasoline.

So, for the sake of your wallet, your car, and HUMANITY, please don’t top off your gas tank. It’s not helping you, and it definitely isn’t helping me. So when your gas tank clicks off, just let it go. Walk away, man. It’s not worth it.