Originally gas caps were simply used as a closure for the fuel tank. In the past years when emission control and safety issues came into focus, gas caps have been improved to provide other features. As an emission control device, locking caps or those that close with a ‘click’ seal the tank and help reduce fuel vapors from escaping into the air. A missing or broken gas cap can emit the equivalent of 30 gallons of gas per year into the air. As a safety precaution these same types of caps are helpful in the event of a collision or rollover. The prevention of fuel leaking onto the roadway or other surface obviously greatly reduces the chance of fire in an otherwise non-threatening crash. The use of locking caps has also helped in the prevention of tampering with fuel tanks.

On newer cars the emission control features the gas cap provides can be the reason a check engine light is on when you‘re sure there‘s nothing else wrong with the car. When the seal has been broken or isn’t correctly sealing the fill tube for your tank, sensors are triggered and your check engine light comes on and stays on with that frustrating glow drivers endure from time to time. The tripped sensors indicate there is an evaporative leak in your fuel system. If this happens, replace the cap as soon as possible. Once the new cap is locked and in place the light should go out, but keep in mind on some models it will take a couple times of locking and unlocking the cap for the vehicle to sense the leak has been corrected.

If your gas cap has been lost or you suspect it’s not working properly it’s important that you replace it immediately. It’s always a good idea to check with your manufacturer’s guidelines when purchasing any aftermarket part for your vehicle ahead of time to make sure there of any specific features a replacement cap may require. Always beware of one size fits all caps; they may not fill the specific safety and emission control needs your vehicle requires. Once you’ve determined any special features or recommendations your car maker may have, a trip to your local auto supply store is in order. It’s unnecessary to purchase a new cap from the dealership. The cap will be much more expensive and it won’t necessarily be any better than what you’d purchase at an auto supply store.

Specific features aside, your auto supply store will search for the correct replacement cap for your vehicle and in most cases it will be in stock. Because gas caps are a fairly common item, most stores carry a significant stock of them. If for some reason it’s not in stock, they can always run the part down for you and direct you to the place that currently carries it.

Once you’ve found the proper cap you’ll install the new one just as the old one was complete with retention rings, if your car has them, to insure you don’t lose the new cap.

And always, whether you’re putting fuel in your vehicle or replacing just the cap, place one hand on the vehicle to discharge any electrical charge you may have built up. Fuel fumes are more flammable than the fuel itself so be careful.