You might have seen a car motor burning and asked, “Is engine oil flammable?” Contrary to the common belief, engine oil isn’t flammable; it’s combustible. This means engine oil will still catch on fire if exposed to a much higher temperature.
Flammability is determined by a substance’s flash point or the lowest temperature that vaporizes a liquid enough to ignite it. Substances with a higher flash point, like engine oils, can be classified as combustible.
Understand the difference between flammable or combustible liquids here.
Table of Contents
- Is Engine Oil Flammable?
- The Flash Point and Ignition
- Conditions Under Which Engine Oil Can Ignite
- What Makes a Substance Flammable?
- Fire Risks and Precautions
- Industry Standards and Regulations
- Engine Oil Flammability and Environmental Concerns
- Frequently Asked Questions
Is Engine Oil Flammable?
As common as they are, many still misidentify engine oils as flammable oil and people continue to ask, “is motor oil flammable?”
For your informaiton, engine oils are actually classified as combustible, not flammable, due to their higher temperature requirement to ignite.
The US Occupational Safety and Health Administration (OSHA) classifies engine or motor oil as combustible since a temperature of around 300 to over 400 °Fahrenheit is required to ignite it.
Flammable substances will only need around 200 °Fahrenheit and an igniter to catch fire. These temperatures are called flash points.
The Flash Point and Ignition
What separates flammable materials from combustible ones is their flash point. This term refers to the minimum temperature that vaporizes a liquid, allowing it to catch fire with an ignition source.
1. An engine oil’s flash point
An engine oil’s flash point, whether conventional or synthetic oil, is registered at >150 degrees Celsius or >300 °Fahrenheit.
In Australian standards, this puts motor oil outside the Class 3 flammability bracket (<60 °C flashpoint), the boundary classification for flammable materials.
Further, Australia comprehensively categorizes engine oils as C2 combustible fluids. This is due to the liquids over 93 °C (199.4 °Fahrenheit) flash point.
2. About flashpoint
The flashpoint of engine oils is determined through the Cleveland open-cup apparatus test, per ISO 2592:2017. Such apparatus is employed when dealing with oils that have over 79 °C (174.2 °Fahrenheit) flash point.
It is worth noting that it is not motor oil burn but it’s the vapor igniting caused by exposure to high temperature. Flash point only involves the first and instantaneous ignition of such vapor without continuing to burn thereafter.
If the flammable vapor burns for five seconds or more, it is to be referred to as the oil’s focal point. Flashpoint also differs from auto-ignition, which does not require an igniter to start a fire.
Common ignition sources may include a hot surface, electrical sparks, friction, impact, and flame. Without these igniters, flammable and combustible liquids will only turn into vapor and likely vanish through the air.
Conditions Under Which Engine Oil Can Ignite
A car engine will normally operate in temperatures ranging from 195 to 225 °F, which means the motor oil in it will not combust in regular engine performance alone.
Engine leaks normally start a fire with motor oil since it allows the leakage to reach extremely hot parts it shouldn’t reach, like the valve covers and exhaust system.
Here are common conditions which can cause engine oil to ignite:
1. Excess heat
While a normal engine temperature is not hot enough to combust motor oil, other components can register excessive heat enough for an ignition. If a leak reaches these hotter parts, it will be enough to burn and eventually catch fire.
An exhaust manifold, for example, normally registers a temperature between 300 to 1600 °Fahrenheit. If your engine runs fast, it will result in hotter exhaust, instantly vaporizing an oil leak and causing fire hazards.
Excessive friction can also register higher temperatures past the engine oil’s flash point. Normally, too much friction can happen if oil levels in the motor aren’t enough, which can result in the engine overheating.
There can be a chance that engine oil is contaminated with other chemicals, such as gasoline. This contamination can result in fire risk since the contaminant has a lower flash point and can be ignited when heat exposure.
Prolonged engine oil usage without proper change accumulates contaminants and debris, making the liquid more flammable than usual.
4. External spark
Continuous exposure by the engine oil to an external spark can lead to it catching fire. It is noted that a spark can reach and exceed 1500 °Fahrenheit. The constant exposure to this temperature significantly above the engine oil’s flash point will trigger a fire.
What Makes a Substance Flammable?
Flammability is rooted in the substance’s molecular composition and structure. It is understood that liquids that easily give off vapor in lower heat are the more flammable substances.
This is because flammable liquids comprise smaller molecules with weaker intermolecular attractions. Lesser heat energy can easily break their intermolecular bonds and transform them into gas or flammable vapors.
- Volatile liquids are an example of substances with weak molecules vaporizing in lower heat.
- In contrast, engine oil, a viscous and thick liquid, comprises stronger bonds of heavier petroleum hydrocarbon base molecules. This composition will require more heat energy to break its intermolecular bonds, requiring higher temperatures to turn them into gas.
Such molecular structures make them less susceptible to evaporation easily, making them a combustible substance rather than a flammable one.
Fire Risks and Precautions
- Identifying potential fire hazards involving engine oil
The car oil flammable state and even diesel oil flammability risk is commonly found in poorly maintained car engines. Leakage usually leads to engine oil burning from hotter motor components.
- Safety measures to prevent engine oil fires
Ensuring that your engine does not leak any amount of motor oil can avoid this risk. You must keep your lube oil from reaching parts where it belongs, as outer engine components can be hot enough to combust such substances.
Additionally, you must store your engine oils in a temperate and dry environment away from the sun to prevent harmful chemical reactions and oxidation.
- Proper handling and storage of engine oil
Whether it’s a newly purchased 3 in 1 oil or used motor oil flammable to higher temperatures, you must ensure they are properly stored to guarantee workspace and car safety. Here’s what to consider when storing your oil products:
- Ventilation– Avoid storing your engine oil in hot and enclosed cabinets; ensure they are in an open, well-ventilated area to dissipate any flammable vapor.
- Proper label– Label and separate your used oils from new ones. They must not be mixed.
- Containment measure– Engine oils are toxic and a fire risk. Always contain your spills and leaks by using sand or other products to absorb them.
- Keep away from igniters– Never store them in places with fire starters.
Industry Standards and Regulations
Three major industry standards regulate the quality and manufacturing of engine oils. They are:
1. ACEA Oil Standard
This standard governs the European Automobile Manufacturer Association. The quality is indicated through a letter and number (e.g., A1, B1, C4). The letter denotes the engine type, while the number indicates the oil performance– a higher number denotes better performance.
2. The SAE Standard
The Society of Automotive Engineers develops this standard for oil viscosity description. The markings are denoted as “00w00”.
The number on the right indicates the oil’s performance at higher temperatures. The higher the number, the better the oil efficiency when hot.
In contrast, the number on the left indicates performance in cold temp. Better efficiency in cold temps is denoted by a lower number.
3. The American Petroleum Institute Standard
The API standard is a criterion for the product’s offered protection against corrosion and oxidation and its dispersive or detergent power.
API standard is indicated through two letters, and the higher quality oils are denoted with a letter further along the English alphabet.
Engine Oil Flammability and Environmental Concerns
Engine oils are known to be toxic air and water pollutants that can have devastating environmental and health effects.
Aside from flammability concerns, engine oil runoffs from leakage and improper dumping find their way to bodies of water and the ocean. These toxic chemicals result in ecological balance, animal and plant deaths, harm to animal migration, and pollution.
Ensuring that used engine oils do not contaminate the soil and water by proper dumping and recycling is a great measure to avoid these serious risks.
Frequently Asked Questions
How can I minimize the risk of engine oil fires?
The key to minimizing engine oil fire risk is consistent and proper car engine maintenance. This will prevent engine component deterioration and ensure no leaks are present.
Regularly changing your oil and maintaining an optimal volume will prevent your machine from overheating and wearing down your important engine components.
What should I do if the engine oil ignites?
Use a carbon dioxide fire extinguisher to suppress an engine oil fire. You should avoid putting out the fire with water as engine oil flammable in water can risk the fire spreading.
In case an engine oil ignites in your car or while driving, immediately pull over and turn off your engine. Do not try opening your hood; you could risk fueling the flame inside. Call the authorities so they can handle the situation safely.
While engine oils are not classified as flammable, they are still a fire risk to be handled with extra care and attention. Knowing at what temperature they are vulnerable to catching fire is critical to prevent any ignition from happening.
Now that you know the correct motor oil flammable classification, you can easily answer the common question, “Is engine oil flammable?”
As misidentified as they are, engine oils are classified as combustible.
Working with Vernon and Ryley has been a great experience for me. Together with the rest of the team, I hope to create reliable and useful information for our readers, no matter where they are and their experience with car maintenance.