Antifreeze in a Gas Tank: What REALLY Happens?! (Explained)

Antifreeze is a vital engine coolant that aids in temperature regulation in your vehicle. Thus, it’s no wonder why most people have one. It can be a great thing, especially if you drive under extreme heat. However, while it works on an engine, you may wonder if it would also work in the gas tank. So, you may ask: 

If you put antifreeze in a gas tank, what really happens? Since an antifreeze regulates temperature, it can do extreme damage if it gets mixed in the fuel and reaches the combustion chambers. If the antifreeze combines with the fuel, it can lead to poor performance and can cause significant damage to the engine.

In the market today, you can find a particular type of antifreeze designed for your car’s gas tank. However, it’s still not ideal to use such. If you run your engine with antifreeze in the tank, you risk many issues.

In this article, you’ll see a walkthrough of all the possible effects of antifreeze in a gas tank, including its downsides. This way, you can understand its risks and deal with your engine if antifreeze gets in the tank.

Without further ado, let’s get into it!

Antifreeze in a Gas Tank

What happens if you put antifreeze in the gas tank?

When you put antifreeze into the gas tank, you can damage the engine. If the car is running, it may not start, and it can even smoke and stall. The antifreeze mayIn addition, the potential damage to the engine if the driver continues to use the car.

The antifreeze regulates the temperature of a car, especially on a radiator, so it keeps a cool temperature in hot weather.

While antifreeze works well on such parts of the vehicle, it won’t be the same with the gas tank. The antifreeze can cause significant damage, especially when mixed with the fuel and burned in the combustion chambers.

Short term effects

The antifreeze immediately takes a toll on the engine. In addition, it generally affects the fuel combustion if the engine is running.

Thus, the short-term effects of putting antifreeze in the gas tank may include severe issues such as engine stalling, hiccuping, and disabling.

Long term effects

Now, if you keep on driving your car with antifreeze in the gas tank, you’ll likely end up with a dead engine that needs thorough repairs.

Since antifreeze affects the engine so much, it won’t take long before your engine permanently shuts down.

Can antifreeze in a gas tank damage an engine?

As mentioned earlier, antifreeze in a gas tank can cause significant damage to an engine. Thus, if you continue driving your car with antifreeze mixed with the fuel, you can end up damaging your car.

For this reason, you must be careful and shut down the engine as soon as you know there’s antifreeze in the gas tank.

When antifreeze reaches the gas tank, it creates a disturbance in the temperature and performance of the fuel system.

Such significant damage can take a toll on the engine’s work as soon as the combustion process continues.

Thus, it can also lead to disabling the engine if the antifreeze prolongs its stay in the tank. For this reason, you need to have the engine fixed immediately.

Don’t hesitate to have your car towed or have the fuel drained, as negligence can lead to severe issues.

How much antifreeze in a gas tank will ruin it?

Even a tiny amount of antifreeze can ruin an engine as it gets mixed with the fuel and burned. 

If you know your tank has antifreeze, don’t try to start the engine to make sure everything is fine. It may operate without problems for a short time, but the longer it runs, the more money it costs you.

You also need to know the type of antifreeze that reached the tank. If it’s an antifreeze designed for a gas tank, you don’t need to drain the tank. However, if it’s the antifreeze for radiators, you need to do otherwise.

Flush the fuel line into the injectors or carburetors by draining the tank. Look for any obvious pollution in your engine oil.

You should also get the engine up to temperature and change the oil and filter after running well. If you’ve done everything else, I’d recommend using a good injector cleaner to be cautious.

Can you tell if someone put antifreeze in your gas tank?

Yes, you can immediately tell if someone put antifreeze in your gas tank. It’s possible since the antifreeze can cause immediate and noticeable effects on the engine.

For instance, if someone puts antifreeze in your gas tank, it can immediately affect the entire fuel system. Some issues you can encounter are engine stalling, hiccuping, and even disabling.

Furthermore, if antifreeze leaks into the gas tank and the engine runs with it, the fuel pump, fuel filter, and fuel injectors will get damaged. As a result, you’ll need to replace such parts.

Every second the engine is running adds up to the potential damage it can get. Thus, it’s important to stop driving as soon as you realized what happened. In addition, it would be best to have your car towed, and the fuel tank drained, as it isn’t something you should skimp on.

How do you get antifreeze out of a gas tank?

The only solution to get the antifreeze out of a gas tank is to drain it entirely and clean it thoroughly. 

Empty the gas tank until it’s empty of fuel and antifreeze. Pure gas should be used to refill the tank. To get any residual water into the gas solution, apply a gas line antifreeze additive. Before refilling the tank, let it run nearly empty.

Suppose you bring your car to an automotive specialist. In that case, the mechanic will likely fix it by draining the antifreeze from the gas tank.

Antifreeze in Gas Tank

How does antifreeze get in fuel?

While some antifreeze gets in the fuel because of an intentional act, some cases are different. For instance, an antifreeze may reach a fuel tank due to a faulty issue within the engine.

When a head gasket breaks, coolant leaks straight into the engine cylinders, resulting in reduced performance and smoke from the tailpipe. 

However, an engine can operate for an extended period in such conditions. Thus it’s normal for engines to run with tiny quantities of coolant seeping into the cylinders.

Whatever the reason is, always remember that antifreeze will damage your engine if it reaches the gas tank. Thus, you should always make sure that this substance is secured and not mix with the fuel.


In a nutshell, you shouldn’t put antifreeze in a gas tank. Antifreeze regulates temperature. Thus, if it mixes with the gasoline and reaches the combustion chambers, it can cause serious harm. If the antifreeze reacts with the gasoline, the engine will run poorly and may suffer substantial damage.

There is an antifreeze specifically developed for your car’s gas tank on the market nowadays. However, using one is still not recommended. You risk a slew of problems if you operate your engine with antifreeze in the tank.

In the end, always keep in mind that antifreeze can cause significant damage to your engine, especially if it reaches the gas tank. Thus, you should always make sure that it is secured and not mixed with the fuel.



Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more