Your Car's Fuel Filler Neck Has Holes At The Top For A Reason

The fuel filling apparatus for your car is a lot more complex than we tend to give it credit for. Every time you fill up your car, it safely transports a highly flammable liquid from the pump into your gas tank (hopefully) without spilling a drop. 

If you've ever taken a look at the filler neck under the gas cap (or under the cover for cars without a gas cap), you've probably noticed some sort of hole or vent right above or around where the fuel goes in. As simple as it looks, it's a vital part of making sure all of that gasoline and the fumes it produces are handled as safely as possible. It also ensures proper air flow when filling.

Gasoline, while sitting in your gas tank, doesn't exist entirely as a liquid. It produces fumes. It's part of the reason why older gas cans for yard tools like lawnmowers can puff up in hot weather. Fumes are why it's important to make sure you're storing your gasoline safely. Well, the gas tank in your car can act the same way if it wasn't for those little holes in the filler neck.

The holes, which are connected through a separate line to the fuel filler neck, vent out gasoline fumes, preventing it from building up in your gas tank. It also allows air into the gas tank. I've replaced gas tanks on cars before, and I've learned that venting is a vital part of the operation (right after I splashed myself with leftover gas from the tank of a 1999 Dodge Neon).

Tanks Inc., a company that makes aftermarket fuel tanks for custom cars and hot rods, puts it very succinctly: "You cannot put fuel into your tank unless you can get the air out... and you cannot withdraw fuel from your tank unless you can let air in."

As with a lot of automotive features like airbags and seat belts, it's a simple enough idea that has vast safety benefits. So the next time you're getting gas, be sure to take a look under the gas cap. Keeping the area free of any obstructing debris is an easy thing you can do to make sure your car runs well and runs safely. After all, keeping your car clean doesn't have any downsides.