What Happens if You Overfill Your Gas Tank?

Many motorists limit their gas station trips since it takes time, effort, and money. The idea is to get the most mileage from your vehicle before having to refuel, and one way to achieve this is by filling the tank with as much gas as possible. So, what happens if you overfill your gas tank?

If you overfill your gas tank, you waste money and potentially damage your car and the environment. Gasoline expands as temperatures rise, and excess fuel can spill into your car’s vapor emission control system and damage it. The gas overflow can also release toxic emissions into the atmosphere.

Read on to learn more about the adverse effects of putting too much gasoline in your vehicle. This article will detail possible outcomes of overfilling your tank, how to avoid it, and what you should do in case it happens.

The Effects of Overfilling Your Gas Tank

The nozzle at the fuel pump automatically clicks and stops pouring gas once your tank has reached its maximum capacity. However, it’s not unusual for people to continue filling their car with gas after hearing that click. Whether they do it to maximize their trip to the gas station or to round off to the next dollar, the effects can be pretty detrimental.

Below are several reasons you should never overfill your gas tank:

Car Damage

It may seem harmless to keep filling your car up with gas as long as you don’t see the fuel overflow from the neck of the tank. However, even if you manage to keep the gas from spilling at the gas station, it can still overflow after you leave.

According to Consumer Reports, a 15° F (-9.4°C) rise in temperature increases the volume of gasoline by 1 percent. So, if you fill your tank on a cold morning, you will have more gas in the tank when the temperatures peak later in the day.

If gas expands enough to make it to your vehicle’s vapor emission control system, it can cause severe damage.

The vapor emission control system keeps the fuel tank’s vapors from reaching the atmosphere during refueling. It works by collecting the vapors with a carbon filter or charcoal canister and then routes them to the inlet manifold for disposal by burning them in the engine.

Vapor emission control systems do not work with liquids, so if they take in gasoline from an overfilled tank, the charcoal canister or other components can become damaged.

A damaged vapor emission control system may trigger your car’s check engine light. However, even if the check engine light doesn’t come on, the damage will keep you from passing the emission test. You may even smell gasoline whenever you’re near or inside your car, making it hazardous to your health.

The charcoal canister in your vehicle’s vapor emission control system can cost anywhere between $200 to $1500 to replace.

Environmental Impact

Without a properly functioning vapor emission control system, the fuel vapors trapped in the gas tank would have nowhere to escape. They will be released into the environment as soon as someone opens the vehicle’s gas cap, contributing to air pollution.

Overfilling your tank with gas can also cause an overflow, resulting in gas dripping down the side of your car and onto the ground.

Gasoline vapors are toxic because they contain benzene and other harmful chemicals. Benzene is a carcinogen, a substance that can cause cancer.

Inhaling gas vapors can also cause immediate health problems, including:

  • Nose and throat irritation
  • Headaches
  • Dizziness
  • Nausea
  • Difficulty breathing

Exposure to vast quantities of gasoline can also be fatal.

Waste of Money

The Clean Air Act aims to reduce gasoline’s negative impact on our environment. Aside from regulating the quality of gas and requiring vehicles to have emission control systems, the law also requires gas stations to have their own vapor recovery systems.

After overfilling your gas tank, the vapor recovery system may take back some of the gas you’ve already paid for to prevent spillage. This means that you’re paying more money for less gas! 

Can Overfilling Your Gas Tank Cause an Explosion?

Overfilling your gas tank can cause an explosion, but only in rare cases. If enough gas overflows or the fuel tank ruptures and causes a gas leak, it can ignite the fuel and explode. However, fuel in an overfilled gas tank will not typically expand rapidly enough to create an explosion.

Fuel is highly flammable, so it doesn’t take much of a spark to ignite it. A cigarette or even an engine misfire can cause fuel to burn. If fuel is ignited, a fire could break out, but the chances of an explosion are minimal, even if the fire makes its way to the gas tank.

Explosions occur when gasses trapped within an enclosed area rapidly expand and build enough pressure to cause a sudden and intense outward release of energy.

A heat source like fire can trigger an explosion. However, fire needs fuel, heat, and an oxidizing agent like oxygen to sustain itself. In the case of a gas tank, it will not have enough oxygen to sustain a fire.

Although gas tanks are enclosed, they are not pressurized. So even if they catch fire, the chances of an explosion are incredibly slim.

How To Deal With an Overfilled Gas Tank

The best way to prevent overfilling your gas tank is by not pumping more fuel into it after the nozzle clicks and shuts off. However, if you accidentally overfill your gas tank, thankfully there are some steps you can follow to deal with it:

Turn the Gas Dispenser Off

If you notice an overfill, you must ensure you are no longer pumping gas into the vehicle. The gas dispenser nozzle’s sensor should automatically shut off and stop pumping gas into your car if it senses the tank is full.

However, if, for some reason, the nozzle fails to shut down automatically, you must turn it off manually.

Clean Up the Mess

Once you’re sure no more gas is flowing from the dispenser nozzle, return the nozzle to the holder and clean up any spilled gasoline.

Many gas stations have fuel spill products readily available. You can ask an attendant for assistance, who will most likely use a sand-like absorbent material to cover the spill.

If you have an old rag in the car, you can also use that to deal with the spill but make sure that you dispose of it properly. Putting the rag back in your vehicle will fill your car’s interior with gas vapors or, at the very least, a foul odor.

Don’t use water to clean any gas residue since it may form a gas slick. If you must use water, mix it with detergent or soap.

Wash your hands thoroughly with non-abrasive soap after cleaning the mess.

It’s best to remove any clothing that’s been drenched in gasoline. If this is not possible, try to remove as much gas as possible from your clothing using a rag or paper towel before driving off. Drive with the windows down to keep the car’s interior well ventilated.

Do not toss your gas-soaked clothes in the washer with the rest of your laundry. Soak it in vinegar and water for at least 30 minutes before hanging it to air dry. Once dry, you can wash it as you usually would.

Get Rid of the Excess Fuel

When your car has too much gasoline, you must lower the fuel level as quickly as possible.

One option is to drain the fuel to prevent gas vapors from reaching your vapor emission control system. If the gas station has a service bay with a lifter, the onsite mechanic should be able to take care of it for you.

It may seem an added inconvenience, but having your fuel drained is considerably cheaper than replacing the car’s vapor emission control system.

If you feel that the ambient temperature isn’t enough to cause the gas to expand, you can start the car and rev the engine until it burns enough gas.

Related: What Color Is Gasoline (And Other Fuels)

Additional Tips When Refueling

Not overfilling your gas tank is just one of many tips you can do to ensure your safety while refueling.

Below are some additional safety reminders when you’re at the gas station:

  • Switch the car off while refueling. Only turn the car on once the dispenser is back on the holder and your gas cap is locked.
  • Secure or remove anything that could cause a spark or fire, such as lighters, cigarettes, and electronic devices.
  • If you’re at a self-service station, touch any metal part of your car to get rid of any static charge before touching the gas dispenser.
  • Stay close to the nozzle in the vehicle fill pipe, and never leave the pump unattended.
  • Return the nozzle to the holder, fasten the gas cap, and close your car’s fuel lid.

Final Thoughts

The hassles of overfilling your gas tank far outweigh any benefits you get from it. Hence, you should refrain from squeezing the nozzle after hearing it click. That click is there for a good reason, and you won’t be able to get that much more gas in the tank before potentially making a huge mess, anyway.

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