Is Motor Oil Flammable? Quick Facts

Is Motor Oil Flammable? Quick Facts

Last Updated on November 2, 2023

Have you started to notice your car is leaking oil, and concerned the leak might cause a fire? Is motor oil flammable?

Motor oil is not a flammable liquid, but instead a combustible. Temperatures need to reach 300° to 400° Fahrenheit for motor oil to combust and burn. In fact, motor oil is among the least flammable fluids with a flashpoint of 302 to 392 degrees.

But this doesn’t mean that leaking engine oil is not capable of catching fire, it just requires a much higher flashpoint to burn. Flashpoint refers to the temperature at which a flammable liquid vaporizes, or is able to ignite.

For example, motor oil that leaks onto the vehicles exhaust manifold has the potential to burn and cause an engine fire.

In fact, an exhaust manifold can reach extremely high temperatures – in some cases, even upwards of 1200° Fahrenheit. This is well above motor oil’s flashpoint, and a recipe for an engine fire.

If you think there’s even the slightest chance that your car could be leaking motor oil, take it to get checked out right away. It’s always better to be safe than sorry!

Now, let’s take a closer look at some of the surprising facts regarding the combustion properties of motor oil.

Let’s dive right in!

Why Isn’t Motor Oil Flammable?

Without getting too scientific, motor oils have long hydrocarbon chains. As a result, they’re difficult to break down. But that doesn’t mean they can’t catch on fire under certain circumstances.

For example, if you spilled some motor oil on your BBQ pit and then lit it, the oil would probably catch on fire.

Motor oil can easily burn when there is the right amount of heat.

What’s The Difference Between Flammable Materials From Combustible Materials?

Different materials can burn in different ways. Some materials, like gasoline, can burn in the air. This is because their vapors are combustible.

Other materials, like motor oil, need to be in contact with extreme heat before they will ignite.

To be considered flammable, an object has to ignite at 200 degrees Fahrenheit. However, oil ignites at a much higher temperature.

The OSHA Laboratory Standard defines a flammable liquid as any liquid having a flashpoint below 100 degrees Fahrenheit.

Whereas a combustible liquid is defined as having a flashpoint at or above 100 degrees Fahrenheit

What is an Engine’s Normal Operating Temperature Range?

A vehicle’s engine is designed to operate within a normal temperature range of 190 to 220 degrees Fahrenheit. However, depending on the make and model of the vehicle, this range may vary slightly.

Engine temperature is regulated by the cooling system, which consists of a water pump, radiator, and thermostat.

Why do Some Engines That Have Never Leaked Oil Catch on Fire?

Some car fires have been caused not by leaks, but instead from a catastrophic engine failure. For example, if a connecting rod inside the engine fractures, the broken parts may crack the engine block.

An engine block that has a crack will allow motor oil to escape and drip onto hot engine surfaces. Surfaces such as the exhaust manifold or catalytic convertor can easily exceed 1200° Fahrenheit. As a result, dripping motor oil on these surfaces will lead to a fire.

Will Leaking Oil Cause Any Other Problems?

If oil is leaking from your engine, it could eventually cause the engine to fail. Avoid this by checking your oil regularly and fixing any leaks as soon as possible.

Motor oil is critical in controlling the temperature of your car’s engine by minimizing friction. If your car is low on oil due to an oil leak, it can lead to overheating or engine failure.

Final Thoughts

Hopefully, we’ve put your mind at ease and you know now that motor oil is not flammable.

However, as highlighted in this post, motor oil under the right heat temperatures can be combustible and will burn.

So if you see or smell oil leaking from your engine, please get it looked at as soon as possible. It’s not only a safety hazard, but it could also lead to some expensive repairs down the road.

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One thought on “Is Motor Oil Flammable? Quick Facts

  1. Avatar
    dan gerene
    September 28, 2022 at 10:41 am

    Some years ago another mechanic was running a new 2.5 Citation (told you years ago) trying to locate a light tapping noise. He had the rocker cover off while doing this on a hot day for some time, the oil on the exhaust manifold lit up. I have also had anti-freeze light up from a pinhole (little flashes) in a heater hose over the exhaust manifold.

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