Is Antifreeze Flammable? Does It Catch Fire?

Coolant is used in engines to prevent overheating. While coolant can be added to prevent it from freezing in extreme cold temperatures (which is highly heat sensitive), antifreeze is not. It is possible for antifreeze to catch fire if it is mixed with water.

Quick answer: Antifreeze is flammable. It can ignite when it comes in contact with heated surfaces. This is because of the presence of propylene glycol and ethylene glycol, which are both flammable alcohols.

Let’s take a closer look at how antifreeze can be flammable.

Are antifreeze and coolant one and the same?

Both terms refer to fluids used in engines to lower temperature but they are different. When temperatures are low, antifreeze is used. Coolant is, however, a mixture between antifreeze (water) and coolant.

In a 50/50 mix, water and antifreeze are used to make coolant. If you live in cold climates, your antifreeze can reach 70%. Your water content will be closer at 30%.

Can antifreeze catch fire?

Antifreeze is flammable. It can catch fire at high temperatures. It can still catch on fire, even if antifreeze has been mixed with water to form a coolant. If antifreeze is ignited with an external ignition source or at high temperatures, the water content will evaporate, leaving only the antifreeze solution.

It is rich in alcohols, such as propylene and ethylene glycol. We all know that alcohol is highly flammable, and will catch on fire if exposed to high temperatures. The antifreeze will ignite just like alcohol when exposed to ignition sources.

Also read: Is DEF Flammable?

Is antifreeze flammable at what temperature?

Antifreeze must be heated to a high temperature, or have an external ignition source like a spark or fire in order to catch fire. This can happen if the engine is heated too much or accidentally.

We must first understand what the terms “flashpoint”, “autoignition temperature” and “antifreeze temperature” mean to determine where antifreeze can catch fire.

Antifreeze flashpoint

Flashpoint refers to the temperature at which fluids can catch fire when exposed to an ignition source. Antifreeze has a flashpoint of 260 °F. This means that if an external ignition source with a temperature of 260°F or higher is present, antifreeze can catch fire instantly.

Antifreeze auto-ignition

An fluid’s auto-ignite temperature is the temperature at which it can ignite itself without external ignition. If the temperature around the ethylene glycol-based antifreeze exceeds 650°F to 750°F, it can auto-ignite and catch fire.

Is ethylene glycol antifreeze flammable

Yes, ethyl glycol can be flammable. The auto ignition temperature for ethyl glycol-based antifreeze ranges from 650 to 750° Fahrenheit. The flashpoint, however, is about 232° Fahrenheit. The temperature at the which ethylene glycol antifreeze turns flammable depends on the amount of water that is added.

A coolant containing 100% ethylene glycol boils at around 360°F to 365°F, whereas a coolant containing 30% water can boil at 224°F to 227°F. When it comes to flashpoint, pure ethylene glycol has a flashpoint of 254°F to 260°F, but when 30% of the mixture is water, the flashpoint rises to 286°F to 288°F. The autoignition temperature does not change significantly due to the complete evaporation all of the water at that high temperature.

Is it too hot to use antifreeze?

Antifreeze can’t be used in temperatures that are higher than 650 to 775 degrees Fahrenheit. This temperature can set off an antifreeze fire. Water-based antifreeze is made from a combination of water and antifreeze (ethylene glycol, propylene or both). The boiling point of the coolant will drop as the coolant’s water content increases while the flash point will increase.

Some believe that a 50/50 water-to-antifreeze ratio reduces the chance of coolant setting fire to extreme heat. Studies have shown that antifreeze’s autoignition temperature is not affected by the amount of water in the mixture. This is because water evaporates rapidly at high temperatures.

What happens if coolant is spilled on my engine?

A fire in an engine is rarely started by coolant or antifreeze. Although antifreeze is flammable, it has a high flashpoint temperature and autoignition temperature. The antifreeze is likely to be secondary rather than primary cause of the flames.

It is important to clean up coolant spillages from the engine. The engine can be damaged if coolant is left on it when the temperature rises. Antifreeze can also cause damage to the electrical components of your engine. Use soap, water and a cloth to remove coolant from your engine.


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Antifreeze, which is flammable, can set itself ablaze. It is more volatile than fuel, so it will likely be a secondary source of the fire. If there is no external ignition source, or temperatures are extremely high, it is unlikely that coolant will catch fire and overheat.

Leaked antifreeze or accidental spillage can cause engine heat up to ignite. There is a risk of a spark if coolant gets in contact with hot engines. If coolant or antifreeze is leaking contact a mechanic.

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