Can Transmission Fluid Catch Fire? You’ll be surprised by the answer!

One of the many joys of owning a car is working on it when something goes wrong. Okay, that may have been sarcastic but it’s all part and parcel of owning a car. Due to the wide range of mechanical components and technical parts, things will go wrong with your motor.

Is Transmission Fluid Flammable

Luckily, most of the time, cars just need simple maintenance to keep them running. From time to time, you may have to top up or change the transmission fluid. Transmission simply refers to the gearbox of your vehicle.

The gearbox uses gears and gear trains to provide torque and speed from the car’s power source (the engine). This is transferred to another device (the wheels). Transmission fluid is used as lubrication on the components of a vehicle’s transmission so that it runs smoothly and properly.

When working with any kind of vehicle fluid, it is important to know whether it is safe or not. One question many ask is if transmission fluid is a flammable liquid or not.

We are here to tell you that transmission fluid is not as dangerous as you may think. While transmission fluid can catch fire, it is reasonably safe so it is unlikely to cause any major fires. Let’s find out more about this common fluid below.

Transmission fluid: What is its flashpoint?

Transmission fluid may be reasonably safe but it can still catch fire. The OSHA (Occupational Safety and Health Administration) defines transmission fluid as a combustible liquid rather than a flammable one. This is due to its flashpoint.

A transmission fluid’s flashpoint is between 302 and 383 degrees Fahrenheit (150 to 195 degrees Celsius). This means that it can catch fire at or above 300 degrees Fahrenheit.

If the liquid is heated up to or above this flashpoint, there are enough vapors being released to catch fire. However, for this to occur, some kind of ignition or spark must be present.

As the flashpoint is above 199.4 degrees Fahrenheit, it is labeled as a non-flammable liquid by the OSHA. For transmission fluid to ignite spontaneously, the temperature needs to be approximately 400 degrees Fahrenheit or 204.4 degrees Celsius.

This auto-ignition means that the fluid can catch fire without any external ignition source. However, the conditions need to be precise for this to happen. 

As you know, 400 degrees Fahrenheit is very hot so, under normal circumstances, this auto-ignition is highly unlikely to occur.

However, it is possible in some industrial environments. Welding and grinding can see byproducts reach temperatures hotter than 400 degrees Fahrenheit. Therefore, if transmission fluid is present, it could auto-ignite.

If you are welding or working with extreme temperatures, always keep transmission fluid separated from the area. 

You should also consider the form of transmission fluid. If it becomes a mist or a type of spray, it could ignite at lower temperatures than 400 degrees Fahrenheit. When experiencing any kind of high heat, try to avoid using transmission fluid in these forms.

Can transmission fluid catch on fire?

As we now know, transmission fluid can indeed catch on fire. But, under normal circumstances, it will not.

Transmission fluid does not burn as easily as other liquids such as lighter fluid or gasoline. Therefore, it needs to be heated to extreme temperatures in order to ignite.

But the truth of the matter is that transmission fluid can catch fire, even though it is not classified as a flammable liquid.

Transmission fuel is light mineral oil. In rare cases, it can cause fires. There have been occurrences where a seal hasn’t been installed properly on a truck and, after breaking under a heavy load, has dumped the fluid over a scorching exhaust crossover pipe.

The high temperatures of the exhaust pipe and the transmission fuel combined, resulting in a blast of flames.

If the fluid runs out in such a scenario, the fire can cease but, as cases like this show, transmission fluid can be extremely dangerous and flammable under the right circumstances. 

What happens if transmission fluid gets burnt?

If you ever experience a burning smell as you’re driving, it can be cause for alarm. While it may not always be serious, it is worth having your vehicle professionally inspected.

One reason why a burning smell may occur is when transmission fluid overheats within the transmission. In this instance, your vehicle needs to be serviced and seen by a mechanic as soon as possible.

The main signs of burnt transmission fluid include:

  • A smoke/burning smell
  • Transmission fluid leaking from the transmission
  • The transmission fluid is darker than its usual red color
  • Having difficulty trying to change gears

As we mentioned above, if this transmission fluid leaks and comes into contact with a hot surface in the engine or exhaust system, it will most likely catch fire.

How to handle transmission fluid safely

Although transmission fuel requires high temperatures to auto-ignite, you still need to be very careful when handling it. Below are some tips to ensure you and others around you are safe when handling this liquid:

  • Keep the fluid away from naked fire sources and high heat to prevent accidental fires. Even a little spray or mists from transmission fluid could ignite when temperatures are under its flashpoint.
  • Store transmission fluid in a clearly labeled package. Ideally, this should be its original container and out of the reach of children and pets.
  • When disposing of transmission fluid, you should place it in a container before dropping it off at a local mineral oil disposal site. Search online for the closest one to you. You can also take it to an oil incinerator for a safe and environmentally friendly option. Another method is to simply clean the fluid and store it in a clean container so you can use it again in the future. However, keep a close eye on its color. If it changes from its original red hue, it may not be reusable. 
  • Check for leaks. This will prevent hazards and a poor driving experience. Some leak symptoms include grinding gears, clunking sounds, noticeable patches of liquid, burning smells, and a delay in acceleration, or less power. If you find a leak, take it to a mechanic as soon as possible.

Is it safe to put transmission fluid into a hot car?

In short, yes, this is safe to do so but it depends on your definition of hot. As a matter of fact, transmission fluid should be put into a car when its engine is running. 

The engine should be running but not for too long. The best time to place transmission fluid into your car is when the engine is idling and the vehicle has its parking brake on.

The reason you should add transmission fluid when the car is already hot is that it expands when passing through a hotter transmission.

Adding fluid to a cold car is not the best option. When you turn the engine on, the fluid will expand but there will be nowhere for it to go. If this occurs, it can lead to a failed transmission and a fluid leak all over the engine.

However, the car shouldn’t be too hot. Remember, the flashpoint for transmission fluid to ignite is around 383 degrees Fahrenheit. If it comes into contact with this heat, it will ignite and set surrounding components on fire.

The good news is that your car should never be this hot (apart from certain engine components and exhaust pipes) so, as long as the engine is running, it should be safe to add transmission fluid to your car.

In Summary

Transmission fluid is not technically a flammable liquid but it can catch fire. Due to its flashpoint of 300 degrees Fahrenheit, this fluid is considered a combustible liquid. But, if you weld or grind regularly, you will meet these temperatures.

By taking sufficient safety precautions, as outlined above, you should never have to encounter transmission fuel igniting.