Oil Smells Like Gas? How to Fix it?

20th Sep,2023

Oil should smell like oil, no matter how many miles your car has. If you smell gasoline in your car while driving, then there might be faulty parts in the car that should be immediately fixed. 

If left unchecked, it could turn into a catastrophe. Gas leaking into oil is unsafe because oil is a lubricant, and fuel can thin it out. You must fix it as soon as possible, or you run the risk of your engine blowing out.

We will explain all the reasons, results, and fixes for this problem, so stay tuned till the end.

There is always a small amount of fuel constantly mixing with the oil. Piston rings and the PCV system play an important role in keeping this in check. So, they could be the cause of this problem if they are not working properly. 

Let us start with a brief discussion of these parts and their functions.

What are Piston Rings?

picture of piston ring

Piston rings are metallic rings that sit on top of the piston, which is positioned right by the cylinder walls. The cylinder acts as a compression chamber for the air-fuel mix. There are three rings in total:

  1. Top Ring or Compression Ring

It seals the combustion chamber and ensures that the air-fuel mix does not leak into the crankcase or the blowby.

  1. Middle Ring

This ring is like an added layer of protection, which functions as the upper ring and the lower ring too.

  1. Lower Ring or Oil Control Ring

It keeps the oil intact in the crankcase and away from the combustion chamber. 

A minute amount of gas slips through the defenses of piston rings, but it is vaporized instantly by the high temperatures of the oil. 

What is the PCV System?

picture of car intake system

PCV stands for Positive Crankcase Ventilation. Its function is to remove the blow-by gases that escape the piston rings and enter the crankcase. These gases will accumulate and turn into sludge. 

They can also increase pressure inside the crankcase, which can blow out gaskets. 

So, the positive crankcase ventilation system acts as a one-way valve. It removes the gases but does not let them enter. The PCV system also does volumes for the environment. 

The emissions, that would otherwise be blown into the atmosphere are now sent back to the engine to be burned. It increases fuel efficiency and is beneficial for the environment as well. 

Reasons Why Oil Smells Like Gas

Let us circle back to the main topic now, which is, what is the reason for oil smelling like gasoline. If you do smell gas, it could be for of the following reasons:

  1. Driving Short Distances Too Often

A small amount of gas mixes with oil at all times. But it gets vaporized because of the high temperature of the oil. The oil can only reach such temperatures when the engine has been running for a long time.

If you drive short distances frequently, then the engine does not get the time to get hot enough. So, the gases don’t get burned and their content increases. 

  1. Rich Fuel Mixture

Engines run on a specific air-gas ratio. When the ideal air-fuel mixture is not created, the engine is said to be running too rich. It happens when the fuel content is much higher than usual. 

This balance is kept in check by sensors in modern cars. So a rich engine could be caused by a damaged mass air flow sensor, O2 sensor, or coolant temperature sensor. 

If the fuel is present in increased quantities, then the combustion chamber will be unable to burn all of it and the gases will travel to the oil pan.  Most engines work in this manner except if you have a powerstroke.

  1. Faulty Fuel Injector

Newer vehicles have fuel injectors, which provide the fuel needed by the engine to work properly. They are controlled by a solenoid, which receives signals from the car’s computer. 

The computer calculates the precise amount of fuel that needs to be released. The solenoid sends a pulse of electricity to open the injectors. 

If the solenoid malfunctions and the injectors get stuck in an open position, fuel could seep down the cylinder walls and into the oil pan. This could be the reason for the gas-like smell.

  1. Damaged Piston Rings

If you read the beginning of the article, then you are familiar with the function of piston rings. They act as a layer of protection between fuel and oil and prevent them from mixing. 

Although piston rings don’t get damaged easily, they are still machine parts and are bound to degrade eventually. And when they do, fuel can enter the cylinders and the oil pan. 

You can do a leak test or a compression test to make sure if the piston rings are faulty. 

  1. Leaks in the Fuel Pump

Locate the fuel pump in your car and check the lines running from it. If there is a leak in the fuel lines, then it means that the fuel is dropping directly on the motor.

Fuel is a highly flammable substance, and getting in contact with a hot motor could spark a fire or blow your engine. So if you locate a leak, repair it immediately. 

  1. Bad Carburetor

A carburetor can be found in older cars. It has been replaced by fuel injectors in newer models, but it has the same function as an injector. 

A carburetor has many parts that are prone to damage. For example, a butterfly valve provides a fuel-rich mixture to help start a cold engine. But a faulty valve will not close and the fuel will keep spilling out into the engine. 

Some other reasons why oil smells like gas:

  • You might smell gas fumes if the gas cap is loose or missing entirely.
  • If the OEM coolant temperature sensor is damaged, then it could relay false information to the ECU. 
  • If you accidentally fill fuel into the oil chamber. 

Symptoms of Gas-Oil Mixture

picture of gas oil mixture

If there is indeed gas in the oil, then you will see the following symptoms:

  1. Dipstick Gas Smell

A dipstick is a stick that you dip in the oil chamber to check its level. So if the oil smells like gas, then to be sure, you can smell the dipstick. If it smells like fuel, then your doubt will be confirmed. 

Also, observe the speed at which the oil drains from the dipstick. If it drops faster, there is excess fuel mixing with the oil. 

  1. Exhaust Smoke

Another way is to check the smoke coming out of the tailpipe. If you see white opaque smoke, it could mean that the combustion system is not working properly.

This will lead to the engine running rich, which means there is fuel seeping into the oil pan. 

  1. Increased Oil Level

The oil level in your car will not rise unless you fill it up. So if you see a rise in the oil level, it means that some fluid might be leaking into the oil pan. More often than not, that fluid is gas. No matter if you use synthetic oil or regular oil doesn’t make a difference

What Happens when Oil Smells Like Gas?

If there is fuel leaking into the engine and mixing with oil, you have got a problem. It can cause a lot of problems if not detected and fixed soon. Some of the issues it can create are:

  1. Reduced Viscosity

Oil is essential for the engine to run, and it also acts as a lubricant to ensure that everything runs like a well-oiled machine! Oil is more viscous than gas and, hence, is more suitable for lubricating machine parts.

But if fuel gets mixed in oil, then the viscosity of oil goes down, and it loses its lubricating properties. This will make it difficult for the car to start in extreme weather conditions. 

  1. Engine Overheating

When the oil gets thinner due to more fuel content, it will become less viscous. This means that oil will not flow smoothly through the engine, making it harder for the engine to cool down. 

This will lead to the engine overheating, which will cause severe damage and give way to many problems, like a blown gasket. 

  1. Risk of Fire

Fuel is highly flammable and can easily catch fire. So, if there is a fuel leak, you should get it fixed. Because it very well may be a question of life or death.

  1. Reduced Fuel Economy

Fuel is required to supply power to the engine. If fuel is getting into the crankcase and mixing with oil, then that fuel is of no use to you anymore. The engine won’t have power, and there will be a bunch of other problems to deal with. 

Over time, this will be a significant waste of fuel and result in reduced fuel economy.

How to Fix this Problem?

This problem, however fatal, can be fixed. Car manufacturers take into account that some parts may degrade after a while, which could lead to this problem. So, they made room for solutions as well.

  1. Take Long Drives

If going for short drives frequently is the cause for this problem, then go for a long drive more often. This will give the engine plenty of time to reach a high temperature and burn the excess fuel from the gas-oil mix. 

  1. Change the Oil Regularly
Picture of oil change

You might not notice it if there is a minute amount of gas present in the oil. But it will keep building up in the crankcase and the gas-oil ratio will increase. So you must change the oil regularly including the filters.

We recommend you use good quality oil like mobile 1 to increase the efficiency of the engine. 

  1. Replace Faulty Piston Rings

Piston rings do not let the gas escape from the combustion chamber and pass into the crankcase, where the oil is. Piston rings are built to last longer so they will rarely be the source. 

If there is no other visible source then check the piston rings and install new ones if they are damaged. 

  1. Install New Fuel Injectors

Fuel injectors supply fuel to the cylinders where it binds with oxygen. Faulty fuel injectors could get stuck and let more gas slip by. This will increase the ratio of the fuel-air mixture. 

The excess fuel will not be burnt completely, leading to smoke and smell. So it is important to install new fuel injectors if they are damaged and causing this problem. 

  1. New MAF Sensors
picture of MAF sensors

MAF stands for mass airflow sensors. They monitor the amount of air passing through the intake valve and into the crankcase. And then they send this information to the electronic control unit (ECU)

A faulty sensor can record wrong readings, which makes the ECU think that there is excess air passing into the cylinder, when in fact the engine is running rich with excess gas.

To fix this issue, you can either clean the existing sensor or install a new one. 


If you have read so far then you know how to identify, diagnose, and fix the problem of oil smelling like gas. 

If you smell gas, investigate thoroughly and pinpoint the source. Get the car diagnosed by a professional and replace the faulty parts. Take the car for regular maintenance and take the necessary precautions. 

Frequently Asked Questions

Some most common questions asked on this subject are answered below.

Is It Bad if Your Oil Smells Like Gas?

Yes, it is extremely problematic if you smell gas while driving. If you smell gas then take your car to the mechanic immediately without further delay. By now you know that fuel leaking into the crankcase can lead to many problems, the worst of which is your engine blowing out. 

This can be expensive to repair, so do not take it lightly. 

How to Diagnose the Source of Gas in Oil?

We recommend taking your car to the nearest auto shop and getting an OBD II check. This might pinpoint the source of the leak. You could also check all the components one-by-one till you find out the one responsible. 

The order of checking the components depends on the ease of getting to those parts. Check the sensors, ejectors, and spark plugs first. Leave the piston rings for last because you have to take the whole engine apart. 

How do you get Gas Out of Oil?

After you have identified and fixed the source of the gas leak, it is time to get the remaining gas out of oil. For this, you have to change the engine oil completely and install new filters. 

You cannot skip any step as they are crucial in the maintenance of the car.

William Johnson

William Johnson is the owner and founder of RatedRadarDetector.org. He writes about car accessories, with his passion stemming from a deep enthusiasm for all things automotive. His website, RRD, focuses on in-depth reviews of car accessories to help people find the best and latest products in the market.