Does your engine oil have a strong smell of gas when you smell the oil dipstick?
This is actually a common problem with gas engines. But how serious is this problem, and should you take any action?
This article will go through why your engine oil smells like gas and how you can avoid it.
6 Causes Why Your Engine Oil Smells Like Gas
- Air-Fuel Mixture way too rich
- You only drive for short distances
- A faulty fuel injector (newer cars)
- A faulty carburetor (older cars)
- Damaged piston rings
- No oil change in a while
These are the most common reasons your engine oil smells like gas, but let’s go a little deeper into them.
Here is a more detailed list of why your engine oil smells like gas.
Air-fuel mixture way too rich
The main cause of why your gas is getting into the engine oil is that your fuel mixture is too rich.
If your fuel mixture is too rich, the combustion chamber won’t ignite all of the fuel, and this will cause the fuel to run through the piston rings down into the oil pan.
There could be several sensors or other problems causing the fuel mixture to get too rich. Read the trouble codes with an OBD2 scanner to see if any stored trouble codes could indicate where you should start your troubleshooting.
Check out our article: Why your engine is running rich to find more solutions to this.
You only drive for short distances
Gas is always running down into your oil pan on most car engines, more or less. When your oil temperature gets high, the gas will come out as vapor from the engine oil.
If you only drive for short distances, the engine oil will not reach a high enough temperature to vaporize the gasoline, and you will fill up your oil pan with gas for a while.
If this happens, replace your engine oil and filter. If you know that you often only drive for shorter distances, it’s recommended to change the engine oil at shorter intervals than normal.
A Misfire happens when the air-fuel mixture is not getting ignited correctly, and the combustion cycle is disturbed. Because the air-fuel mixture is not getting ignited, the gas can wash your cylinder walls, which will cause the compression to be lowered, and more blow-by through the piston rings will happen.
This can cause the gas to pour down through the piston rings and fill your oil pan with fuel.
You can learn more about misfires here: Misfire symptoms and causes
A faulty fuel injector (newer cars)
Fuel-injected vehicles have small injection devices that provide the engine with the fuel it needs. These injectors are operated by a solenoid, further controlled precisely by a computer which lets just the right amount of fuel inside the cylinders.
Since solenoids are mechanical, they can often malfunction. If the solenoid gets stuck in the open position, gasoline will find its way inside because the substance is watery and mixes with the oil.
In the excessive amount that flows out, the gasoline will eventually seep down in the oil pan and mix with the oil as your car is running.
Faulty carburetor or settings (older cars)
Cars with carburetors are different. The fuel mechanism is handled by a diaphragm and controlled by the gas pedal mainly. Since that is too mechanical, the butterfly valve that controls the airflow can get stuck, which will let the fuel in according to the mixture ratio
That will also let gas get into the oil and cause this problem. Similar to fuel-injected cars, the excessive gasoline will go down into the oil pan and mix with the oil.
Bad piston rings
If your piston rings are bad, more fuel will run through the combustion chamber into the oil pan. However, this is not a very common problem, and it’s tough to repair because you have to take the whole engine apart, so I recommend checking the other things on this list before.
No Oil Change for a while
There might not be anything wrong with your vehicle, other than you haven’t changed your engine oil for a while.
Very old engine oil with a lot of sluggish inside of it can smell a lot like gas. If you know that you haven’t changed your engine oil in a while, it is time to do it.
If you have no idea, if the engine oil is recently changed, check your service report manual or call your authorized dealer.
Hi, I’m Magnus, the owner and the writer of Mechanic Base. I have been working with cars for 10 years, specialized in diagnostics and troubleshooting. I created this blog because I was tired of finding false information on the web while looking for repair information. I hope you enjoy my content!