Will Gas in Oil Harm Engine? – Understanding the Risks

Written by

Charles Bolte


Vernon Hoppe 

will gas in oil harm engine

Oil and gas are both essential car fluids, and you can’t operate your vehicle without one or the other. But what if you mix them? Will gas in oil harm engine?

Gas mixing with oil affects the oil’s viscosity or thickness. This impacts the oil’s ability to lubricate the engine parts. Problems like engine damage can arise when the oil cannot fully protect the engine.

What Happens When Gas Mixes With Oil in an Engine?


Engine or motor oil is a fluid primarily used for lubrication. Meanwhile, gasoline or petrol is a combustible substance that provides power or fuel for engines.

As they are entirely different fluids, they should be kept in separate compartments within the vehicle. However, should gas get into your oil, the immediate result is a change in viscosity – the oil becomes thicker or thinner than it should be.

So, is it bad that the oil viscosity is affected? It is for the long term, and here are some of its effects:

1. Short-term effects of gas mixing with oil


Gas or fuel in engine oil usually does not lead to immediate harmful effects or damages – especially if the amount of gas mixed in is minimal. Indeed, it’s even normal to have small amounts of gas mixing into the oil.

However, if there’s so much gas leaking into the oil, your engine can become a fire hazard and may even cause the engine to smoke if you let it run too far. That’s because gas is combustible or a fire-causing substance.

Excessive gas leaks can also lead to a flooded engine with gas and oil mixed. That can lead to many problems, like the inability to start the car.

2. Long-term effects of gas mixing with oil


While a bit of gas mixed with oil in the car isn’t immediately damaging, it does when you let the problem persist. The more gas leaks into the oil, the more drastic the change in thickness or viscosity.

If the oil isn’t the right thickness, it cannot lubricate and protect the engine parts. The oil level and pressure are also affected.

All these can then lead to reparable to permanent engine damage, including bearing wear, which, either way, can be costly to address.

How to Tell Gas is in Oil

Because the gas in engine oil causes problems in the long run, you must be aware of the signs so you prevent damage. For instance, you need to know what gas mixed with engine oil will look like, smell, what color of smoke it will emit, or other symptoms:


  • Gasoline smell in oil: One of the most common indicators is a gas smell in oil. Oil doesn’t have a strong smell, especially when new. Meanwhile, fuel has such a potent odor you can detect it immediately when you’re changing the oil pan, checking the dipstick, or even while driving.
  • Low Oil Pressure: Fuel mixing with oil usually makes it thicker than necessary, leading to low oil pressure.
  • High Oil Level: Typically, oil decreases over time, so you need to top up sometimes. Thus, if you check with your dipstick and see that it’s more than it should be without adding or changing oil, gas could be mixed into the oil.
  • Rapidly Decreasing Gas Level: As the oil level increases from gas leaking into it, the gas level decreases. Thus, you might notice you’re topping up your car with more fuel than usual.
  • Thick, White Exhaust Smoke: When there’s gas in oil, the car could emit thick, almost cloud-like smoke with a distinctively opaque white color. That’s due to the fuel not getting burned off.

How Does Gas Get In Oil?

Besides knowing the symptoms, you must know the various reasons why gas can get into oil. Often, the causes are serious and would need professional help.

1. Carburetor problems


Most old car models have carbureted engines. Their fuel systems use a carburetor to help mix air and gas to create power for the vehicle.

If a carburetor has a problem or too much gas goes into it, the fuel can leak into the oil pan. One way to know that the carburetor is the issue is to find a blackened spark plug or to listen for knocking sounds in your engine.

2. Issues with the fuel injectors


While classic cars use carburetors, newer units opt for fuel injectors. As the name implies, they’re like syringes filled with liquid, which is pressurized or high-pressure fuel.

When the fuel is needed, a plunger pushes the gas out of the injector so it fires out like mist into the combustion chamber. This mist is easier to burn, so the fuel injector system is often more efficient and precise than carburetors.

However, if those injectors have holes or damages, the fuel can leak. That escaping gas can then flow into the oil pan, mixing with the engine oil.

3. Old piston rings


A piston is an engine component that appears as a moving cylinder. It has piston rings, one of which is the oil ring. This oil ring, present even in a small engine, helps restrict the engine oil and gas to their respective compartments.

However, if the oil ring or other piston rings get worn out, the seal used to keep those fluids from each other is broken. This then allows the gas to escape and mix with the engine oil.

4. Misfiring engine


Converting fuel into power requires a combustion reaction, wherein a perfect mixture of air and fuel is ignited. This occurs within engine cylinders. Sometimes, though, the process doesn’t proceed as flawlessly as it should, resulting in a cylinder or engine misfire.

Many scenarios can cause a misfire. For instance, there could be a broken spark plug or ignition coil. Whichever the reason, some gas left unused or misplaced by the misfiring could leak into the oil pan.

5. Human error


There’s also a chance that instead of putting engine oil, you poured gas instead. Although the chances of that are minimal, it is not impossible. If you happen to do that, change your oil ASAP.

Troubleshooting the Problem

It’s hard to know why fuel or gas gets into oil unless you do some troubleshooting, which you’ll learn in this section. Plus, you’ll get some tips on how to fix gas in oil.

1. Let the oil burn off


Will gas in oil burn off? It does. That’s why even though gas mixing with oil is normal, you may not notice it often because the fuel has already evaporated from the long drive.

That also explains why if you drive only short distances, you better notice if gas accumulates in your oil pan. The engine hasn’t burned it off, so it stays there and emits odor or causes thick white smoke.

Thus, you can try burning off the oil first to see if it’s just an accumulation from the lack of long trips.

2. Change oil


If you can’t take a long drive to burn off the oil, try changing it. This way, you won’t keep exposing your engine to oil with the wrong viscosity. Moreover, while driving with the new oil, you can assess if it’s just the usual gas-got-into-the-oil scenario or something more serious.

3. Consult a mechanic


Once you’ve tried burning the oil off or changing it and the problem persists, seek a mechanic or technician immediately. They are better equipped with tools, skills, and knowledge to determine the cause behind your car’s gas mixing with engine oil.

Moreover, they can properly advise you on a solution. For instance, they can tell you what parts need replacement and how much they can cost.

How to Prevent Gas Contamination In Oil

Identifying the reason why gas is in your oil and fixing that reason can be a hassle. Thus, it’s much better to prevent it from happening. So, what can you do to keep gas from mixing with your car’s engine oil?

Simply put: regular maintenance and proper care. Have your car checked or serviced once or twice a year for underlying issues. In that way, you’ll know if some parts are getting worn out and could cause potential problems.

Also, drive your car on longer trips. As you see above, the shorter the drive, the harder it is to burn off fast that coincidentally got into your oil.

Frequently Asked Questions


Is It Safe To Drive On My Car With the Gas and Engine Oil Mixing?

If only a small amount of gas gets into the engine oil, it should be safe to drive your car. You might even burn off the gas while doing so. However, if it’s too much or the problem persists, get your vehicle checked, as there could be a more severe issue.

How Often Should I Change My Engine Oil To Prevent Gas Contamination?

You should change your engine oil to prevent gas contamination according to your car’s recommended duration. Although most recommend 3,000 miles or three months, the actual period depends on the vehicle, with some cars driving as far as 10,000 miles before needing to change the oil.

Does Synthetic Oil Smell Like Gas?

Synthetic oil doesn’t smell like gas, especially when new. Thus, if your engine oil smells like gas, you should immediately conduct some troubleshooting to identify and solve the underlying problem, if there is any.


Will gas in oil harm engine? As much as possible, gas and oil should be kept separate. That’s because when these two liquids mix, they result in a thicker substance that won’t protect the engine and its parts well.

If you think gas is mixing with your oil, you should burn it off, change it, or seek professional advice. There may be an underlying issue, like a problematic carburetor, and you should fix or replace that soon to prevent further problems.

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