Engine Oil Smells Like Gas – 5 Main Reasons

Written by

Charles Bolte


Vernon Hoppe 

engine oil smells like gas

You open your car’s hood to check the oil level, and the question on your mind is, “Why does my oil smell like gas?”

Well, engine oil smells like gas because it may have mixed with fuel. This may be because of a rich fuel mixture, faulty piston rings, or prolonged changing of the oil.

While it’s common and usually not a cause for concern, this article explains the possible causes and signs that it’s becoming a problem and should be fixed.

Basics of Engine Oil and Its Function in a Vehicle


To get a clear picture, it’s best to first understand why your car needs engine oil.

  • Lubricates the engine parts to minimize friction and reduce wear and tear
  • Prevents corrosive acids that are generated during combustion from damaging the engine
  • Adds a protective layer to the cylinders and pistons to properly seal them.
  • Flows throughout the engine, cleans it from impurities that would otherwise cause clogging, and carries them to the oil filters

Engine oil is stored in the oil pan, attached to the bottom part of the engine. When there is a blow-by (fuel-air mixture leaking through the pistons or cylinder walls), you’ll get some gas mixed with oil in car, causing a fuel smell.

When Does Gas in Engine Oil Become Too Much?

So, is it bad if your oil smells like gas? A bit of gas getting into oil and causing the smell is not uncommon; however, when the gas volume exceeds 2.5%, it becomes too much.

Here are signs that the gas in oil car engines is becoming a cause for concern.

Signs That Your Engine Oil is Contaminated With Gas

These are some of the fuel in engine oil symptoms:

1. Noticeable Gasoline Smell


Among the first signs you’ll notice is that the oil smells like gasoline.

When the fuel smell in oil is strong enough to leak through the vents, you might notice that as you drive, your car smells like gas.

2. Dipstick Smelling Like Gas


Another tell-tale sign is when you check your car’s oil level and notice the oil dipstick smell like gas.

Gas in oil look like thin and runny oil. So if the latter drips off the dipstick faster than usual, gas is mixed with the oil in the car.

3. Increasing Oil Level


If you have not filled up your oil recently but notice a rise in the oil pressure gauge on the dashboard, then some liquid has found its way into the oil pan. Most likely, something has caused the fuel to mix with oil.

4. White Smoke at the Exhaust


White smoke from the tailpipe can be caused by a couple of things, such as excess fuel not burning properly in the combustion chamber or internal coolant leakage.

It can also be one of the gas in engine oil symptoms.

Reasons Why Engine Oil Might Smell Like Gas

Possible reasons why your oil smells like gas include the following:

1. More Fuel Than Air for Combustion

The perfect air-to-fuel ratio for proper burning in the combustion chamber is 15:1. But sometimes, the engine injects more fuel than air into the combustion chamber, causing the former to not burn properly. This is known as a rich fuel mixture.

As a result, some gas will escape through the piston rings, end up in the oil pan, and mix with the motor oil.

In this case, it’s necessary to check the sensors in your car and see if they need fixing.

2. Faulty Piston Rings


Usually, piston rings don’t damage easily. But, if they get worn out or stuck for some reason, they’ll be the cause for gas mixing with oil as the combustion gas will enter the oil sump.

When you notice the engine not performing how it’s supposed to, excessive oil consumption, and white smoke coming from the exhaust, there could be some issues with the piston rings.

3. Driving for Short Distances Frequently

Gas can enter the oil pan and evaporate as you drive. But for the oil to be hot enough to vaporize the gasoline, you must be driving the car for long enough.

So if you only drive for short distances, the engine temperature might not get high enough to vaporize the gas, hence the gas smell.

4. Engine Misfiring


Engine misfiring results from the air-fuel mixture in the combustion chamber not igniting correctly due to faulty spark plug wires, bad ignition coils, vacuum leaks, among other reasons.

When the engine misfires, it lowers compression and makes some of the gas-air mixture leak through the rings, which causes gas to get in oil pans, thus, the gas smell in oil.

5. Faulty Fuel Injectors


Some cars have fuel injectors controlled by the car’s ECU to regulate the amount of fuel that gets into the cylinders.

In case of a system malfunction or a defect in the fuel injectors, some gas will flow into the oil pan, so the oil smells like fuel.

For instance, GDI engines operate by spraying fuel directly into the cylinders. And since their injectors are subject to more heat and stress, and the piston crown design may be poor, they increase the chances of fuel mixing with the GDI engine oil.

Potential Risks of Gas Contamination in Engine Oil


  • Fuel mixing with engine oil or oil dilution does not just result in a gasoline smell in the oil. It also causes it to lose its viscosity and become weaker and unable to handle more friction.

But what does it mean for engine protection? The parts that are more exposed to friction – such as the crankshaft and rod bearings – will become less protected and prone to wear.

  • Contamination of the engine oil causes the dilution of additives that prevent the wear of moving parts by spreading a film on them. The additives cushion and prevent the parts from grinding against each other.

When these additives are diluted, their anti-wear abilities are compromised.

  • Exposure to wear will cause damage to car parts and eventual engine failure.
  • Fuel dilution in oil can cause an increase in oil oxidation, which can lead to corrosion of the internal engine parts and the formation of varnish and sludge deposits.

Steps to Address and Fix Engine Oil That Smells Like Gas

Here’s how to fix gas in oil issues:

#1. Diagnose the source of gas in the oil.


You can use these methods to find out what’s causing the gasoline smell in oil.

  • If your car shows the check engine light on, you can use an onboard diagnostics (OBD) scanner to read the Diagnostic Trouble Code (DTC) and find out the specific problem. A mechanic can assist you in case you don’t have the tools.
  • You can also find out if faulty piston rings are causing the smell of gas in oil by performing a compression test. It will determine if the pistons can efficiently compress the air-fuel mixture in the combustion chamber.

If you don’t have a compression testing kit, buy one or visit a professional mechanic for help.

#2. Get gas out of oil


Delayed or irregular oil changes will not only leave the oil smelling like gas but will also make it dirty and contaminated.

Change the engine oil within the miles or duration recommended in the owner’s manual, and you might notice a difference after oil change.

Prevent future issues

After diagnosing the issue and getting the gas out of the oil, perform the necessary maintenance. This could mean replacing the parts causing the gassy smell, like the fuel injectors, piston rings, oil filter, and pan.

Consider cleaning the fuel system to remove all debris as well.

Frequently Asked Questions


What should engine oil smell like?

Fresh engine oil is well-refined and does not have any distinct smell. However, when it mixes with other elements like coolant and water, it will change its appearance and develop a scent. If it comes into contact with fuel, synthetic oil smell like gas.

In case your engine oil smells like exhaust, check the cylinder head gasket and see if it’s damaged.

Can I continue driving if my engine oil has a gas smell?

Yes, you can continue driving, since the effect on the engine will not be immediate. However, it is best to diagnose and have the issue fixed as soon as possible because prolonged driving of a car with gas in oil symptoms is not good for your health or the engine’s.

Will gas in oil harm the engine?

When oil mixes with gas, it loses its viscosity and will not lubricate and protect the engine as it should. So, eventually, the gas in oil damage engine parts and can cause failure.

When should I consult a mechanic for a gas smell in my engine oil?

As soon as possible. Oil smelling like gas often indicates bigger problems, and you don’t want them to fester and get worse.


When the engine oil smells like gas, it will get your attention, especially when it’s a distinct smell that might be getting you worried.

But you can always refer to this article to know the signs, causes, and what to do if there is too much gas in the car oil.

If the processes seem complex or you tried handling it yourself but the issue persists, you should always visit an experienced mechanic for help.

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