Did your engine oil have a strong smell of gas when you replaced your engine oil?
This is actually a pretty common problem when it comes to gas engines. But how serious is this problem and how do I fix this issue and prevent it from happening again?
In this article, we will go through the causes of why your engine oil smells like gas and how you can avoid it in the future.
Causes of why gas is getting into the oil
Your engine contains cylinders and pistons. The pistons contain piston rings which will seal the combustion chamber from the crankcase. If the fuel mixture inside the cylinder chamber won’t ignite correctly or the piston rings are worn, the fuel can flow down into the oil pan.
However, even after all that sealing, some small amount of fuel getting into the engine oil is actually very normal and nothing to be worried for. That happens as you drive your car routinely as the engine is constantly receiving fuel and the oil is constantly being circulated during the combustions.
This problem arises when either, if your car’s fuel injectors get stuck in the open position, spilling gasoline or if your carburettor is letting interrupted supply of fuel even when the gas pedal is not being depressed.
Here are the 6 most common causes of why the gas is getting into the oil
1. Fuel mixture 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 there are any stored trouble codes which could indicate where you should start your troubleshooting.
Normal causes of rich fuel mixture are the Mass air flow sensor, Coolant temperature sensor, O2 sensor, MAP sensor and the intake air temperature sensor. Go through the links to our post about the specific sensors to learn more about them.
2. You do only drive for short distances
Gas is always running down into your oil pan on almost all car engines, more or less. When your oil temperature gets high, the gas will vapour out from the engine oil. If you do only drive for short distances, the engine oil will not reach enough temperature to vaporize the engine oil and you will fill up your oil pan with gas for a while. If this happens you should replace your engine oil and filter. If you know that you do often only drive for shorter distances, it’s recommended to change the engine oil with shorter intervals than normally.
3. 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 very difficult to repair as you have to take the whole engine apart, so I do recommend to check the other things in this list before. A way to check the piston rings is to do a compression test or a leak down test.
A Misfire is happening when the air-fuel mixture is not getting ignited correctly and the combustion cycle will be 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.
5. A faulty fuel injector (Newer cars)
Fuel injected vehicles have small injection devices which 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 and if the solenoid gets stuck in the open position, gasoline will find its way inside because the substance is watery, and mix with the oil. The gasoline, in the excessive amount which flows out, will eventually seep down in the oil pan and mix with the oil as your car is running.
6. Faulty Carburettor or settings (Older cars)
Cars with carburettors 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 air flow can get stuck which will let the fuel in according to the mixture ratio. That will also let the gas get into the oil and cause this problem. At that point, similar to fuel injected cars, the excessive gasoline will go down into the oil pan and mix with the oil.
What does it mean when we say that gas is mixing with the engine oil?
Have you ever realized that when you are getting your car’s engine oil changed, you get a strong smell of gasoline as the old oil pours out? Do you often wonder why that happens? Since gas and oil are the two active ingredients that are fed to your car’s system, it is possible that the gas may be getting into the oil which is why you are getting the smell of gasoline as you change your car’s engine oil or just take out your dipstick to check the oil level.
While it is normal for a small amount of gas getting into the oil, too much of oil dilution with the gasoline can become a major problem. If the smell is so strong that it feels like the gasoline is flushing instead of oil when getting the oil changed?
Symptoms of oil and fuel mixture beyond the normal amount
If you are unsure whether the mixture of gas and oil isn’t normal, here are a few symptoms and signs you can look for that can tell you whether there’s some problem with the car or not.
- You can smell a strong odour of fuel as you are driving the car
- Your car emits an opaque white smoke from the exhaust rather than a clear smoke
- Your dipstick shows that your oil is either overflowing or the level is increasing without actually adding any oil
- Your dipstick smells more like gasoline than oil
- The oil on your dipstick drops off like water droplets
- The oil pressure gauge shows low oil pressure
- You notice that during changing the engine oil, the oil seems not so vicious
If you encounter any of these symptoms, it may be that there’s an excessive amount of gas getting into the oil in your engine which isn’t normal. A rather easy way to tell if your car is using too much fuel is that your car will emit thick white smoke.
That is due to the fact that fuel that is not burnt properly during the combustion cycle will tend to ignite later when on its way out the cylinder. Also, since oil is viscous and gasoline is not if you realize that your engine’s oil is too thin than it should be, even after a long time of use, there’s a high chance that it’s the gasoline that is changing the viscous properties of the oil.
How do you tackle the problem?
Too much gas getting into the oil in your engine is never a good sign and so the first thing you should do is immediately get your car to be checked by the mechanic for the symptoms above if you do not have the knowledge yourself. If everything looks okay it might be your piston rings that are worn out. The job of these seals is to keep the oil from the oil pan from getting inside the cylinder and keeping the gasoline from dripping into the oil pan.
These seals are worn out over time and need to be replaced. The best sign to look for, which should tell you about the piston rings is to check the smoke your car is emitting. If the smoke is thick and black, it means that your car is burning oil. If the smoke is thick white, that means your car is running rich and burning too much gasoline.
After getting your piston rings checked and replaced, change your engine oil to prevent engine damage.
It’s recommended to make a compression test to check your piston rings sealings. Here is a video of how to make it:
If you do only drive for short distances, it’s common that you will get a lot of gas into your engine oil and in this, you have to replace the engine oil immediately and do engine oil changes more frequently than normal if you will continue to drive for only short distances.
Read the trouble code memory for any signs of broken sensors or other things that will cause the engine to run rich.
If you have any other questions you are welcome to apply a comment down below and I will answer your questions as soon as possible.