4 Problems a Loose Gas Cap Cause

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Gas caps are generally not something most people think about when you are having car trouble. After all, what harm could one damaged little piece of plastic do to your car?

A loose gas cap can cause and contribute to many large problems down the line. These issues can include wasting gas and money and causing harm to the environment and a person’s body. This can also badly damage a car’s inner systems, such as the engine and emissions system.

4 Problems a Loose Gas Cap Cause

Obviously, not every problem your car experiences can be contributed to your gas cap. Your car is a very complicated machine that can run into issues because a speck of sand got caught in the wrong spot. But here are a few issues that can accompany a leaking gas cap.

What is a Gas Cap?

A gas cap is a small but important part of your car. Also known as a fuel cap, the gas cap’s purpose is to simply keep dirt and debris from getting inside the gas tank. It also seals the tank so that your emissions system can reuse fuel vapors that would otherwise be released into the atmosphere.

The gas cap is one of the few pieces of your car that you interact with often. Every time you fuel up your car with gas, you must remove it and then replace it. It is then no surprise that over time, the gas cap experiences wear and tear.

The seal can break, the plastic can crack, the screw-in can be stripped, or you can just lose the cap. Whatever the reason, when a gas cap is damaged, it needs to be replaced.

1. Money (NOT) Well Spent

Having a loose gas cap, or missing it altogether, will cause your car to lose fuel. Even if it is only a tiny crack in the seal, the fuel vapors will escape. This means you will be getting fewer miles for your buck. If you find your fuel tank emptying faster than usual, it might be a good idea to check your gas cap.

Along with losing miles, you also lose money with each wasted mile. Leaving the cap as it is can reduce your fuel efficiency by 1-2%. It may not sound like a lot, but over time that will cost you a good chunk of change. With the recent spike in gas prices, you do not want to be spending money on gas that you are not even using.

2. Environmental and Physical Harm

It should be no surprise that those escaped fumes can cause harm to the world and the people around you.

While limited exposure to such fumes should not cause serious damage, long periods of exposure can. Gasoline vapors, when breathed in, can cause a variety of problems that can range from headaches, coughing, difficulty breathing, convulsions, coma, and heart failure.

Inhaling these dangerous vapors can also allow chemicals to enter the bloodstream, which can cause damage to body tissue. These issues can also apply to animals, whether they be pets or wild. No one wants their dog to have difficulty breathing because it spent some time in the garage with fuel vapors.

Adding to the damage to living creatures, gas vapors are made up of alkanes (such as methane, ethane, and propane) and benzene. All of these chemicals add to environmental issues such as global warming and contaminated water.

Contaminated water can damage aquatic species as well as our fellow man. It can also kill aquatic plants.

Most of this damage happens slowly and over time, but all of it is irrevocably changed. There is no fix for damage caused to your body by gasoline fumes, so you had the best end the problem as quickly as possible.

3. Damage to Your Car

A loose or missing gas cap will allow dirt and grime to get into your fuel tank. The dirt can contaminate your fuel injectors and cause damage to them. This can cause engine misfires. Misfiring engine cylinders can damage your engine significantly. On top of that, if you are driving during a particularly bad misfire it could result in an accident.

Those previously mentioned escaped fumes can trigger an error or damage the control system of your emissions system. Along with that, your vapor recovery system will be used up more quickly and will have to be replaced in order to pass an emission test.

4 Problems a Loose Gas Cap Cause

In most modern-day cars, there is a fuel injection system that relies on pressure to bring gasoline into the combustion chamber. A leaking gas cap throws off the programmed required pressure and will make your engine begin to run lean.

Running lean means that your car is not using gas but trying to use air as its fuel. This will cause your car to have less power, run sluggishly, or not even turn on.

4. Can Ruin More Than Your Tank

Another thing that a loose or broken gas tank does is allow dust, dirt, and other particles to get inside the gas tank, which can, over time, ruin the gas tank, the pipes, and other places the gas goes inside the car. So the little problem that has one thing needing fixing now has many parts inside your car getting ruined over time.

You can be building up the dirt inside these pipes and the tank, making less and less room for your gas and also not allowing the gas to flow properly. The gas carries the dirt into many parts of the car, and it can ruin the fuel line, and potentially the internal combustion engine and the transmission. Those are not easy things to replace or repair, but for cheap, you can replace a gas cap.


The easiest way to prevent any damage from happening is to keep an eye on your gas cap. It is something that you will constantly interact with whenever you refuel. Check the seal, look for any visible wear or tear, and make sure the cap is not lost when it is screwed in.

The first and easiest sign of a faulty gas cap is the smell of the escaped gas. If you can smell gas inside or outside your car, it is a good idea to check the cap.

If it is damaged, then replace it. It is never a bad idea to have a replacement cap ready if you ever damage or lose your cap. Replacement caps are not expensive, running between five and twenty dollars.

As for actually replacing it, there is no need to hire a mechanic. Gas cap replacement is one of the few items in the car that you can fix yourself. A mechanic should only be required if any serious engine issues arise or if a new cap does not resolve the smell.