Is Radiator Coolant Flammable? The Details Guide


Safety is a top priority in the automotive sector, from the factory to the consumers. If safety is compromised for any reason, it’ll cause severe hazards like burns, physical injuries, and even loss of life. For example, the radiator coolant is an essential liquid to cool the engine and prevent overheating.

Since cars use several liquids that can catch fire and burn, you may wonder, is radiator coolant flammable? Here, we’ll discuss whether antifreeze is flammable and answer some trivial questions on this subject. So, grab a seat and a cup of coffee.

Is radiator coolant flammable

Understanding Radiator Coolant

Radiator coolant, also known as antifreeze, is a liquid solution used to regulate the temperature of vehicle engines. It ensures that the engine does not overheat in high temperatures or freeze in extremely cold conditions. Coolant achieves this by dissipating heat more effectively than just water and lowering the freezing point of the solution in the system.

Is Radiator Coolant Flammable?

Radiator coolant is a flammable water-based fluid. It is water-based but is both toxic and flammable because it is formulated with some flammable compounds like ethylene glycol and propylene glycol. With this in mind, you should be cautious when using radiator coolant.

However, do not fret because radiator coolant or antifreeze is flammable. There’s nothing to worry about. Some folks argue that engine coolant is not flammable because it contains water, and an accessible fire extinguisher. Let’s get this straight, while radiator coolant is flammable, it’ll hardly ignite fire unless the fire gets to it.

Radiator coolant is a 50/50 blend of antifreeze and water. But, even with the 50/50 water content, the coolant is still a flammable liquid. So, can coolant catch fire?

Can radiator fluid catch fire?

As explained above, radiator coolant is flammable and can catch fire and burn. However, several parameters, like temperature, can cause engine coolant to catch fire and burn. For instance, Antifreeze can auto-ignite at a temperature of 650 to 800 degrees Fahrenheit.

The truth is, it’s likely impossible for a car to heat up to this temperature unless it is already burning.

Is 50 glycol flammable?

A 50% glycol antifreeze has a boiling point of 223 degrees Fahrenheit and a low freezing point of 35 degrees Fahrenheit. Unfortunately, a 50 glycol is flammable; despite being a water-based fluid, it’ll catch fire once it contacts it. In any case, it doesn’t auto-ignite.

Is Coolant the same as Antifreeze?

One of the questions we get in our garage is, is coolant and antifreeze the same? The simple answer is NO, but they are related. Coolant is the liquid in your radiator that prevents the engine from overheating through its circulation during regular operation. In contrast, antifreeze is a solution in the engine coolant that prevents it from freezing in extreme cold weather conditions.

We have repeated 50/50 several times in this article. So, let’s explain what we mean by this 50/50.  Coolant is 50 percent water and 50 percent antifreeze. However, it’s not always 50/50. For instance, you may need 30% water and 70% antifreeze in extreme cold weather conditions.

On the other hand, antifreeze is formulated with propylene glycol and ethylene glycol. Also, it contains additional additives that prevent rust buildup in the cooling system. Antifreeze comes in a variety of chemical formulas and colors. Therefore, it is essential to use only the recommended product.

Do not use straight water in your radiator to cool your engine. Water expands, boils quickly, and freezes in extremely cold temperatures. In the same manner, do not use only antifreeze in your vehicle. Instead, always use a 50/50 antifreeze and distilled water. Or better still, add a premixed engine coolant.

You can get distilled water, antifreeze, and coolant at auto parts stores and gas stations.

What is the flashpoint of coolant?

We can determine how flammable a liquid is from the flashpoint. The higher the flashpoint, the lesser it is to ignite or support fire, and vice versa. 

The flashpoint of antifreeze is 232 degrees Fahrenheit (111 degrees Celsius). This is the highest degree a liquid can form vapor and hold fire. The higher the degree, the harder it is to support fire. The baseline is, coolant cannot auto-ignite fire because it has the highest flashpoint. Burning antifreeze or white smoke usually results from fire from a short circuit or gasoline.

To determine how unlikely it is to auto-ignite fire, compare antifreeze’s flashpoint of 232 degrees Fahrenheit with petrol’s flashpoint of 40 degrees Fahrenheit.

What is the auto ignition temperature of antifreeze?

The auto-ignition temperature of a substance is the temperature at which it can ignite spontaneously, without an external ignition source like a flame or spark. Here are the approximate auto-ignition temperatures for the common components found in antifreeze:

Ethylene glycol:

The auto-ignition temperature of ethylene glycol is considerably higher than its flash point, generally in the range of 399 °C to 427 °C (750 °F to 800 °F).

Propylene glycol:

The auto-ignition temperature of propylene glycol, another component sometimes found in antifreeze, is around 371 °C to 399 °C (700 °F to 750 °F).

It is crucial to note that these temperatures are much higher than normally encountered in a typical vehicle operating environment. Nevertheless, understanding these properties can assist in implementing safety measures, especially in industrial settings or during the disposal process of these substances.

Is it okay if you spill coolant?

Coolant is highly toxic and flammable. So, it is not okay to spill it. It can be dangerous sometimes, especially if you spill it on a hot exhaust pipe or manifold. However, if you accidentally spill coolant, it’ll remain on the surface until you wipe it out. Coolant does not evaporate. Depending on the coolant color, you’ll see a greenish, reddish, yellowish, or purple color when the coolant dries up.

coolant spilled out

Is engine coolant dangerous to humans?

Engine coolant is deadly to pets and humans. In addition, it contains a toxic property – ethylene glycol, an odorless and sweet-smelling substance. Ethylene glycol is commonly used in many mechanical processes because of its high boiling and lower freezing points.

It doesn’t have much difference from alcohol, but it has a vast difference in human reaction if swollen. If a small amount of the substance gets into the human system, the body will metabolize it as if it’s alcohol without causing any damage to your cells.

However, if a large amount is taken, it’ll form acidic chemicals. This will change the acid/base balance in the body and cause severe damage to the nervous systems, heart, and lungs. Besides, it can also cause kidney failure. Antifreeze can lead to death within 72 hours if swallowed. 

Final words

You have learned that Antifreeze or radiator coolant has a flashpoint of 232 degrees Fahrenheit or 111 degrees Celsius. So, you’ll no longer ask, is radiator coolant flammable, or does antifreeze burn? Engine coolant burns when it gets in contact with fire. However, it can also auto-ignite at a temperature of 650 to 800 degrees Fahrenheit.

While focusing on radiator fluid flammability, kindly note that it is dangerous to humans and animals. So, always keep it from your pets and kids. If you spill it on the floor, wipe it immediately because its sweet smell can attract pets and kids.

Lastly, always drive with the proper amount of radiator coolant to prevent engine overheating and rust buildup in the water galleries.

Solomon Osuagwu

Osuagwu Solomon is a vetted auto mechanic with over ten years of experience in the garage and five years of experience as a service writer. He prides himself in writing accurate information on professional repair guides, DIY repair guides, buyer’s guides, comparisons, and car reviews. If he’s not in his repair garage, he’s writing automotive blogs to help car owners and fellow mechanics to troubleshoot and proffer solutions to several car problems.

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