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How to Clean Black Stuff Around the Gas Cap Door?

Are you tired of getting your hands covered in black grime every time you are refueling your car? If so, I understand — having a dirty gas cap door can be extremely annoying! Luckily, it is also a straightforward part to clean up!

To clean a gas cap, follow these steps: First, remove the gas cap from your vehicle. Use a mild detergent and warm water to scrub away dirt and debris. Rinse thoroughly, ensuring no soap residue remains. Allow it to air dry completely before reattaching it securely to your gas tank.

Cleaning your gas cap is a simple process that helps maintain your vehicle’s fuel system. Start by locating the gas cap on your vehicle and removing it. Inspect the cap for any visible dirt, grime, or debris. To clean it thoroughly, fill a bucket or basin with warm water and add a small amount of mild detergent. Submerge the gas cap in this soapy water and use a soft brush or cloth to gently scrub away any dirt or residue. Pay extra attention to the cap’s threads and seal.

After scrubbing, rinse the gas cap thoroughly with clean water to remove any soap residue. Ensure that there is no moisture left on the cap before reattaching it to your gas tank. Tighten the gas cap securely to maintain a proper seal. Regularly cleaning your gas cap can prevent contaminants from entering your fuel system, improving your vehicle’s overall performance and fuel efficiency.

How Do I Clean the Black Stuff Around the Gas Cap Door?

Cleaning the gas cap door is extremely easy, and you can do it successfully at home. However, it is essential to note that cleaning the gas cap itself at the same time can be hugely beneficial. Follow these steps for the best results!

What do I need to clean a gas cap door?

Gather all the materials you will need before starting the job and get ready to get your hands dirty!

  • A petroleum-based lubricant
  • A silicone-based solution
  • Aerosol gunk remover or degreaser
  • An old rug or cloth

Cleaning a Gas Cap Door Step-By-Step

1. Use the multi-surface grease remover 

Before proceeding to clean the gas cap itself, it is essential to clean both the gas cap door and the surrounding area. Cleaning the gas cap alone might cause some of the fuel residuals to fall in the tank. To start removing the black dirt from the gas cap’s surrounding area, spray it with a multi-surface, all-purpose grease remover.

Opt for a spray or aerosol degreasers so you can easily focus on such a limited surface without spilling over the side of your car. Dilute the product, so you have a blend of four parts of water and one piece of chemical remover to avoid damaging the painting. The degreaser won’t need shaking, stirring, or, after applying, scrubbing.

2. Wash it with a hose

After spraying the degreaser on the gas cap door, allow it to rest for a few minutes for the best results. You can see the grease slowly starting to melt as you allow the chemicals to work. Without touching the black grime with your bare hands, use a hose to remove both the compound and the dirt. While they will come off without issues, you should ensure that there are no chemical residues left on both the gas cap area and the side of your car. 

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3. Unscrew the gas cap and place it on a rug

Now that the surrounding area is back to its natural color and completely dry, it is time to clean up the gas cap. Unscrew the cap and move it onto a stable surface that you don’t mind becoming dirty or damaged. Whether you have picked your driveway or worktable, it is recommendable to protect the surface with newspapers or an old rug.

4. Use petroleum-based lubricant spray

Start by applying or spraying the petroleum-based lubricant over the gas cap. Ensure to cover any area, even the difficult-to-reach screwing mechanism. Pick up your old cloth or rag and spread the lube across the surface through a scrubbing movement. By allowing it to work for a couple of minutes, this chemical will melt any hardened grease. Proceed to wipe the gas cap clean and repeat this step if necessary.

5. Use silicone-based spray

After you have cleaned the gas cap of the residues of the petroleum-based lube, cover it with a silicone-based spray. The first chemical will eventually damage the plastic of the gas cap if you have failed to remove it properly. Instead, the silicone-based spray is a great solution to ensure that the gas cap remains protected from other substances as well as wear and tear.

6. Reinsert the cap and rinse the area

While screwing the gas cap back on, ensure that it does not show resistance. If you can reinsert it smoothly, it means that the mechanism is free of debris. Proceed to rinse the whole area with a hose to ensure that any residual chemicals and grease have entirely gone.


The procedure to follow to see your gas cap door and surrounding area clean is easy and straightforward, but keeping in mind these safety features can make your job safer.

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  • Ensure that the engine is off – a heating engine can quickly react with the chemicals you are using and making the whole procedure much more dangerous.
  • Stay in a ventilated area – you should only proceed to use these chemicals in a well-ventilated area that benefits from fresh airflow. Both a driveway and garage are optimal choices.

Issues Caused by a Dirty Gas Cap

Dirty gas cap doors are out of sight for most of the day, and we usually end up forgetting that grease can build up in it, too.

Moreover, some severe damages can derive from a dirty gas cap door. While it is easy to clean when the dirt first appears, the grime can extend to the fuel cap over time, making it difficult to open it and close it properly. 

Even worse, if the grease and dirt end up on the gas cup itself, you might be facing a much bigger issue. Indeed, it is likely that the residues contaminate the fuel and settle at the bottom of the tank, plugging the gas pump or filter. Having to replace these parts of your car might be expensive, both in terms of money and time.

Instead, cleaning the gas cap door promptly as soon as it gets dirty is a quick and easy task that can save you a lot of frustrations later on.

What Is the Black Stuff Around the Gas Cap Door?

First off, what is the black stuff that you are about to clean? In most cases, it derives from residual fuel build-ups, and it is a mix of mildew and grease. If you are feeding your car ethanol-based fuel, you should be aware of the characteristics of this substance. 

Ethanol is commonly added to fuel to optimize its burning rate, increasing your car’s performance and mileage. However, ethanol tends to attract water and humidity particles from the surrounding environment. 

With ethanol-based fuel sitting in your tank most of the time, it is reasonable that moisture will build-up around the gas cap. Since this area does not benefit from a steady airflow, the moisture will quickly turn into black mildew.

Additionally, the gas cap door is the part of your car that is continuously in contact with fuel, aside from the engine itself. However, unlike the engine, the fuel residual on this appliance tends to sit undisturbed for days or months. Without proper maintenance, this debris will spoil and turn to grease. 

Final Thoughts

Cleaning the gas cap and the gas cap door are tasks that you can complete in under an hour. While we might keep postponing the cleaning day because this area is not one of the most visible ones, keeping your gas cap door clean and free of debris is essential. Indeed, failing to provide it with regular maintenance can lead to contamination of the gas in the tank.

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