Is Brake Fluid Flammable? Everything You Need To Know

As a car driver, you probably don’t give much thought to brake fluid and what it is. As long as your car stops when you want it to, all is good, right?

But that stop couldn’t happen without this essential hydraulic fluid. So, if you think more about it, other questions may arise, like, is brake fluid flammable?

Brake fluid is flammable; if exposed to flame, it will catch on fire and burn. However, it burns at high temperatures, so it is generally not the initial cause of a fire.

Keep reading to learn everything else you wanted to know about brake fluid!

Is Brake Fluid Flammable

What Is Brake Fluid? What Is It Used For?

Brake fluid is a hydraulic fluid used in brake and clutch applications for various vehicles, including cars, light trucks, motorcycles, and certain bicycles.

Most brake fluids currently in use are glycol-ether based. However, silicone based brake fluid and fluids made with mineral oils are also available.

Types Of Brake Fluid

The four main brake fluid types are classified as DOT 3, DOT 4, DOT 5, and DOT 5.1. The DOT stands for Department of Transportation since most brake fluids are manufactured to meet standards by various domestic and international organizations and government agencies.

Other standard-defining agencies include the ISO (International Organization for Standardization) and SAE (Society For Automotive Engineers).

The differences between the four fluid types are defined by their primary ingredient and other characteristics like boiling point and viscosity, which can impact performance levels.

DOT 3, 4, and 5.1 are glycol ether-based, and DOT 5 is silicone-based. The higher the DOT number, the higher the boiling point. DOT 5.1 was developed due to a lack of acceptance of silicone-based brake fluids - it maintains the performance advantages of DOT 5 but is below the 70% silicone threshold. 

In addition, the color of brand new DOT 3, 4, and 5.1 is yellow-amber, and for DOT 5.1, it is purple.

Is Brake Fluid Flammable?

Brake fluid is flammable due to the characteristics of its primary ingredients, although the extent is based on its formulation.

Most modern brake fluids are glycol-ether based, with the minority being silicone-based, and both have been shown to burn, but only at a high temperature.

The glycol-ether fluids burn at lower temperatures when compared to the silicone-based ones.

How Flammable Is Brake Fluid?

The flammability of brake fluid depends on whether or not it is glycol-ether based or silicone-based.

The flashpoint of brake fluid ranges from 210°F to 375°F (99°C to 190°C), with the former lower in that range than the latter. In addition, the auto-ignition point (where it will spontaneously combust) for brake fluid is very high, ranging from 540°F to 675°F (282°C to 357°C).

And if ignited, the burn will be similar to vegetable oil, supporting a low-grade flame. However, it will not be as explosive as volatile fluids like gasoline.

What Is The Brake Fluid Flashpoint?

The brake fluid flashpoint is in a temperature range of 210°F to 375°F (99°C to 190°C) and is ultimately determined by the specific formulation of the brake fluid.

Compare that to the flashpoint of gasoline, which is -45°F so that gives you some perspective on brake fluid's flammability.

Is DOT 3 Brake Fluid Flammable?

DOT 3 brake fluid is flammable since it is glycol-ether based but burns at higher temperatures (flashpoint in the lower range of 210°F to 375°F).

In addition, the dry boiling point of common DOT 3 brake fluids is just over 400°F (205°C). Therefore, it is more flammable than DOT 4 and DOT 5 brake fluids.

Is DOT 4 Brake Fluid Flammable?

DOT 4 brake fluid is flammable since it is glycol-ether based but burns at higher temperatures (flashpoint in the middle range of 210°F to 375°F).

In addition, the dry boiling point of common DOT 4 brake fluids is just under 450°F (230°C). Therefore, it is more flammable than DOT 5 brake fluid and less flammable than DOT 3 brake fluid.

Can Brake Fluid Start A Fire?

Since brake fluid is a flammable liquid, it can start a fire. However, this will only occur at very high temperatures since its auto-ignition point is generally in the range of 540°F to 675°F (282°C to 357°C).

Environmental factors will also impact the actual temperature of ignition.

How Flammable Is Brake Fluid

Is Brake Fluid Dangerous?

Since brake fluid frequently contains diethylene glycol, a poison that, if ingested, can cause death, coma, metabolic acidosis, and kidney failure, it is considered toxic and dangerous.

In addition, inhalation of an excessive amount of fumes could lead to cough, nausea and vomiting, convulsions, or possibly death.

Therefore, if any amount of brake fluid is consumed or inhaled, seek medical assistance immediately.

Furthermore, brake fluid can cause damage to various surfaces it contacts.

Is Brake Fluid Corrosive?

Brake fluid is a highly corrosive liquid, and if it is ever spilled, it should be cleaned up immediately to prevent any physical damage on the surface it was exposed to.  

Does Brake Fluid Ruin Metal Or Eat Aluminum?

Fresh brake fluid will not ruin metal or eat aluminum. However, because brake fluids with glycol are hygroscopic or water-absorbing, it’s possible that over time as the fluid absorbs water, it could ruin metal or eat aluminum.

Does Brake Fluid Damage Paint?

A glycol based brake fluid can resemble paint thinner and strip away the paint on your vehicle, causing bubbling, chipping, and flaking. So use brake fluid carefully around your car and if you spill any on its protective coating, clean it off immediately.

Can Brake Fluid Burn Your Skin?

Brake fluid will not burn your skin. It will only cause mild irritation if exposure occurs. But just to be safe, clean up any contacted areas immediately.

How To Dispose Of Brake Fluid

How To Dispose Of Brake Fluid

Brake fluid is considered hazardous waste and should never be disposed of by dumping it into a sink, toilet, septic tank, storm drain, or onto the ground. Instead, you should take old brake fluid to your local waste management treatment center for proper disposal.

What Happens When You Mix Brake Fluid And Chlorine?

Chlorine is already a dangerous substance, and when mixed with certain other substances, it can create a multitude of reactions. And brake fluid is one of those.

The reaction of is quite interesting because when initially combined, it doesn’t appear anything will happen.

Then within a minute or two, suddenly, the reaction occurs and creates either excessive smoke, a small fire, powerful flames, or an explosion, depending on the balance of chlorine and brake fluid added and the container used.

Definitely not something you want to try at home.

What Other Car Fluids Are Flammable?

Just about every fluid part of a motor vehicle can be flammable if the conditions are right. It depends on temperature, the presence of oxygen, and whether there is an ignition source present.

So that means the following additional car fluids could be flammable:

After seeing this list, you may start thinking that you don’t want to drive your car anymore. But fear not, cars are designed to withstand a lot of things, and there are unique situations where these become fire hazards.

If you have concerns, read each related article to learn more. So keep on driving!

Final Thoughts

Now, not only do you know the answer to the question - is brake fluid flammable but you are armed with many facts about brake fluid, and other types of automotive hydraulic fluid, that will make you a superstar at your next trivia night!

Thank you for taking time out of your day to read this article.