Is Motor Oil Flammable? Does it Catch Fire?

Motor oil is the stuff we put in our cars to keep them running. We know that motor oil is associated with combustion, but is it the actual motor oil that gets set on fire.

The answer to this complicated question is yes, but only at a certain temperature.

That’s right, motor oil has a flashpoint of 419 degrees celsius. This is the temperature at which it sets on fire. This means that you’ll have to get it extremely hot before it catches fire at all.

This means that motor oil is technically not deemed as flammable by the motor oil society. Simply put, you’ll have to get this oil super hot before it will set alight.

This means that you won’t have to worry about wielding a cigarette around it, although we would still recommend that you avoid having any oil near this substance.

So what is the best method of handling motor oil? How much ignition do you need for it to be set ablaze? Is it safe to use motor oil with your particular brand of car?

When it is safe and when is it dangerous to use motor oil? How much of it do you need to cause an explosion?

Well, if you want the answers to these questions and a lot more, then we would suggest that you keep reading.

We’ll discuss all the properties of motor oil, as well as how difficult it is to set alight and whether or not you can be certain of it catching fire when you are using it.

How Flammable Is Motor Oil?

The main reason that motor oil is not classed as a flammable liquid is purely because it burns at such a high temperature. It will take 419 degrees of heat to get this substance to catch fire, which is well outside of the danger radius of most ignitors.

The flash point should not be confused with the auto-ignition point, which is the temperature at which this oil will spontaneously combust. For motor oil, this temperature is traditionally a lot higher.

This means that motor oil will not be ignited by a random source like a lighter or a cigarette. You can probably accidentally drop a lit cigarette in motor oil and not have to worry about it catching fire.

The Reason Why It Isn’t Flammable

This is only a technicality surrounding the definition of the word ‘flammable’. Items that are considered flammable only set fire at a certain temperature.

Lots of flammable liquids are short chain hydrocarbons that release vapor very slowly, which allows them to be ignited at much lower temperatures.

These molecules in flammable substances simply take a loss less energy to separate. When this separation occurs, one of the molecules is lost in the form of vapor.

This vapor is then ignited by a flame, which is what causes it to spontaneously combust.

Motor oil is a much thicker liquid, which causes it to be a lot more viscous, with long chain hydrocarbons that are a mix of various different molecules.

There can be as little as 18 hydrocarbons in one molecule of motor oil, which makes it much harder for them to separate and much less combustible.

This is the reason why you need a lot more energy and force in order to break up the molecules, which is why there is less vapor and it requires a lot more energy to heat up. However, this does not mean that your motor will not combust at all.

This is why you should consider motor oil a ‘combustible’ rather than ‘flammable’ substance. It will just take a lot more heat to set your motor oil on fire.

This is why you should still be careful when operating naked flames around your motor oil.

How Hot Does Motor Oil Have To Be To Catch Fire?

Motor oil has to get to around 400-degrees before it catches fire. If you are working with this substance, you should try your best to limit the amount of heat that you’ll have coming in from lighters and cigarettes.

You should try and keep it away from all intense heat sources, if possible.

How To Store Motor Oil Properly

You’ll need to make sure that when you are not using it that you’ll be storing oil correctly, as you’ll want to reduce the chances of things catching on fire.

Make sure that your oil is properly ventilated, as this will obviously result in vapors building up which will increase the chances of it catching fire.

If you have a single bottle of motor oil, then this might not be a problem, but we would recommend that you air it out regularly.

If you have a single bottle of motor oil, then we would recommend that you stand it in a bucket of sand.

This will be to absorb leakages, which could result in your widespread oil spillages which will increase the chances of fire damage.

Does Synthetic Motor Oil Catch Fire?

Synthetic oil is actually much less flammable than motor oil and you’ll need a lot more heat to set it on fire.

So if you are worried about leaving your motor oil unattended for long periods, then we would recommend that you opt for synthetic oil rather than the genuine stuff.

If you run synthetic motor oil at 400 degrees for around an hour, you will only see a reduction of 4% of oil in your tank. This is amazing compared to the 30% loss of oil that you’ll get for genuine oil.


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