Motor Oil Smells like Gas ? Symptoms, Causes and Fixes

If you perceive a gas smell in oil, you will most likely have a gas-oil mixture. Gas and oil are the primary fluids in a car that ensures the smooth running of your vehicle. When you notice oil smells like gas, you should not take it lightly because there are consequences.

You need to understand the symptoms of gas in engine oil and the leading causes to enable you to solve these issues and also prevent future problems. The cause of a gas-oil mixture can be due to faulty engine components or driving short distances at all times. In this article, we’ll explain what causes oil-gas mixture, common symptoms of oil and gas mixture, what will happen if oil gets into the oil pan and how to fix oil smelling like gas.

What causes oil to smell like gas?

Knowing why your engine oil has a strong gas smell will efficiently enable you to prevent gas-oil odor and fix it if the gas has already found its way to the crankcase.

symptoms of gas in engine oil

Short Distance Drive: if you don’t usually drive long-distance, like driving interstates, you’re most likely to perceive gas smell. When you drive a long distance, the oil pan will heat up to a certain degree and provide heat that will vaporize the small amount of gas that finds its way to the crankcase.

 On the other hand, driving short distances will not allow the crankcase to heat up to the state of vaporizing the excess gas in the crankcase. If most of your driving is within the city, then you have to be driving long distances. If driving long distances is out of your schedule, you have to consider changing your engine oil more often.

Faulty Fuel injectors: When it comes to the air-fuel mixture, the fuel injectors play a significant role. The fuel injectors send the right amount of fuel-air mixture to the cylinder walls that the combustion chamber requires. Fuel injectors have a built-in solenoid that is controlled by your car’s computer. The car’s computer will send the calculated amount of fuel needed by the engine to your fuel injectors. If you have a faulty fuel injector, it’ll spray an excessive amount of fuel to the cylinder walls, which will eventually find its way to the crankcase and cause the gas-oil smell.

Faulty Piston Rings: The Piston rings work as a sealing agent that prevents oil from passing to the combustion chamber and fuel from getting to the crankcase. Like every other car component, the Piston rings can wear out over time. Worn-out Piston rings will allow fuel passage to the crankcase, which will result in an oil-gas smell.

Engine Misfire: Many factors can cause your car’s engine to misfire, including damaged fuel injectors. Regardless of the misfire, there are chances for gas to enter the crankcase during a misfire. During an engine misfire, all combustion cycles will be affected, hindering adequate air-fuel ignition. During the engine misfire state, the air-fuel mixture will not be completely burnt, which could cause the unburnt fuel to get into the crankcase.

Dirty Fuel: At one point or the other, some filling stations sell dirty patrol. This dirt can be from the truck that supplied the gas, storage well, or as a result of unrefined petroleum. When you pour such gas into your vehicle, once this gas gets to the combustion chamber for igniting process, some of the gas will not burn due to the dirt in the gas. Unburnt gas will find its way to the crankcase.

Running Rich Fuel: All car engines are designed to run with a specific air-fuel ratio. If the fuel injectors or carburetors are sending more fuel than the required amount, the combustion chamber will not burn all the fuel, which will result in fuel passage to the crankcase. There are many reasons for a rich mixture. Some of the common causes can be damaged MAP sensors, bad mass airflow sensors, or bad oxygen sensors.

No Oil Change: let’s get this straight! Not changing your engine will not cause the oil to smell like a motorcycle or gas smell directly. It is imperative to note that a small amount of gas entering your engine oil will not impact,  and it might not be noticeable. However, if this small amount of gas passage is built up in your crankcase and you fail to change your oil regularly, you will start noticing the gas smell in the engine oil once the fuel passes 2.5% of the oil quantity.

Pouring gas instead of oil: Someone might sporadically pour gas in an engine oil port instead of engine oil. One of the common reasons why one might pour gas instead of motor oil is mixing up containers. Some folks use containers to buy both gas and engine oil. They might mistake these containers for each other. Hence, you should avoid using random containers.

Stuck Fuel injectors: The fuel injectors are designed to close themselves automatically after sending the right amount of fuel to the combustion chamber. If the fuel injectors become faulty, they might get stuck open and pour excess fuel into the cylinder walls. When this happens, you’ll notice oil smells like a lawnmower. If the excess gas in the crankcase gets too much, it can cause catastrophic engine damage.

What are the Symptoms of an Oil-gas Mixture?

Like every other issue with your vehicle, some symptoms show you have a faulty component in your car. If too much fuel mixes with the motor oil, few signs will pop up, indicating that you have some gas volume in the oil pan.

can gas in oil damage engine

Strong Gas Smell: when excess fuel finds its way to the crankcase, like in the case of a stuck fuel injector, a strong gas smell will pop up. In some rare cases, the smell may be so strong that you’ll perceive it while driving; you might not even need to check the motor oil level before perceiving the smell.

White Exhaust Smoke: whenever you have issues in your combustion chamber, the common and sometimes first symptom you’ll notice is white smoke from your exhaust pipe. As a result of rich fuel, there are chances that unburnt fuel is finding its way to the crankcase.

Dipstick Gas Smell: Another gas smell symptom is the ‘dipstick gas smell’ when you check the oil level, take the dipstick close to your nose, and perceive it. If it smells like fuel, it means some fuel has found its way to the oil pan. Watch the oil as it drops off the dipstick. If the oil drops faster, it tells you to have an oil-gas mixture.

High Oil Level: Your motor oil should not increase significantly in any case. If there is much increase in the oil level, it indicates some fluid is entering the oil pan. These fluids can either be water due to burnt cylinder heads or excess gas that makes its way to the oil pan. You can easily tell if the increase in the engine oil is water by the oil color.

What will happen if oil goes into the crankcase?

There are no instant effects for an oil-gas mixture. However, if much gas finds its way to the crankcase or a small amount of gas stays in the crankcase for long, there will be some consequences that you’ll need to be aware of.

Affecting Oil Viscosity: Oil is more viscous than fuel, making it more suitable for lubrication than gas. If a large amount of gas enters the oil pan or small gas leaks into the oil pan and stays there for long, the oil will lose its viscosity.

Fast Wear and Tear: Once the motor oil loses its viscosity and lubricating power, your internal engine components will begin to wear out faster. Oil Viscosity prevents internal engine components from wearing out. Therefore, preventing or solving the oil-gas mixture will save you hundreds of dollars in repair costs.

Overheating Engine: If the oil loses its lubricating power and becomes less viscous, it will not cool down quickly. An Overheating engine can stop running. It will also cause severe engine damage, like a blown head gasket.

Lost of Gas and Reduction in fuel Economy: If excess fuel finds its way to the crankcase, then you’re losing a tremendous amount of fuel. When this happens, you will have less engine power and a significant drop in your fuel economy.

How do you fix oil that smells like gas?

My candid advice here is that people who design engines are aware of oil dilution. Likewise, the people who produce the motor oil. The formulation of motor oil is such that it provides adequate protection when it is diluted up to the point of normal operation. The things you can do to manage oil dilution is to go for a long drive regularly, a couple of hours with lean burning on the highway to sustain optimum temperature operation.

That will do the job nicely. It will help purify the motor oil in a matter of burning in which at stake, will evaporate out the excess fuel in the crankcase. But apart from that, it’s just like burning excess heat. Alternatively, you can change the oil a bit frequently if you only make these short trips. If the engine longevity is crucial to you, you need to realize that a harsh operating environment for the oil is not what you want to imagine.

One of the harshest things you can do to the oil down there in the crankcase is to cold-start, drive to a station 10 minutes away and get back 10 hours later. That way, you’re killing you’re engine. You need to change your oil twice often.

PS: I did not make this up. Many car manufacturing companies recommend changing your motor oil a bit more frequently in harsh operating environments or as advised by the dealer. It’s not routinely communicated that driving short distances constitutes a harsh operation for your car. You should regularly check your oil level. If the oil level climbs far above the standard gauge, don’t forget to get professional advice.


Is it bad if your oil smell like gas?

If your engine has a gas smell, it is most likely you have an oil-gas mixture. If the gas stays for long in the crankcase, it will affect your oil lubricating power and make it less viscous. When this happens, your engine’s internal components will wear out faster.

Will gas evaporate out of gas?

If you notice oil smells like Reddit, which indicates a gas-oil mixture, you might want to ask if the gas will evaporate out of oil. Yes, gas will evaporate out of oil when you have a long-distance drive that will heat the crankcase enough that it will allow the gas to escape as vapor.

Is 2-year-old gas still good?

Gas degradation usually starts from the get-go, a gas that is a month or two old is still okay, but when it gets to 1year old, it is recommended that you change it. However, allowing your gas to stay up to 2 years old, can cause engine problems like fuel injection problems. We recommend always use good quality gas can for carrying the gas for disposal.

Is it okay to mix old gas with new gas?

Old gas will lose its potency once it gets up to a year, leading to rough running and engine misfiring. So can you mix old gas with new gas? Yes, but you should ensure that the amount of old gas you intend to mix with new gas should not be more than 25% of the total amount of gas in your gas tank.

Final Thought

At this point, you must have known how to fix issues associated with gas getting into an oil lawnmower. With this article’s help, you can quickly tell the causes of oil smelling like gas and what will happen if gas goes into the crankcase.

You might notice just one or two of the outlined symptoms when gas goes into the crankcase. Once you see any of these symptoms, you want to do the necessary things like driving a long distance and doing a regular oil change.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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