What Causes Oil to Leak into The Spark Plugs?

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What Causes Oil to Leak into the Spark Plugs

You should not ignore it if you notice that the oil is leaking into your spark plug. It’s a severe problem, and if not repaired faster, it could lead to an engine fire. If you just bought a car, you might not recognize the problem quickly. So in case, you notice the symptoms below, call your mechanic immediately. 

How to Identify The Problem?

1. Blue Smoke Coming From the Tailpipe

To realize how serious the oil leakage is, check the tailpipe. If you see blue smoke coming from it, then take your car to the mechanic immediately. Blue smoke shows that the condition is extreme.

2. Poor Fuel Economy

If the oil keeps on leaking into the spark plugs, it means you will have to keep on refilling. If you notice that your fuel consumption has increased, it could be due to leakage.

3. Decreased Engine Performance

The leakage affects combustion efficiency. As a result, engine performance reduces significantly. 

4. Possible Engine Misfire

In some extreme cases, affectation in combustion energy usually causes a misfire. The misfire is noticeable, and you should call the mechanic immediately. 

5. Back-Fire

The fuel particles often burn in the combustion chamber. If there is a leakage, it doesn’t burn in the combustion chamber but instead enters the exhaust pipe. Since it comes with high energy, it causes mini-explosions. 

6. Gas Smell

You can quickly know if the oil is leaking into your spark plug if you notice a gas smell from the exhaust pipe. Mostly, you will see oil and gasoline mixture coming from the tail. It comes with a bad smell as a result of lousy combustion. 

Maybe you’ve been asking, why are my spark plugs wet with oil? Many factors can contribute to leakage. The leading causes include

a. Valve Cover Gasket

The main aim of a valve cover is to ensure that the oil remains on the cylinder head and prevents it from spilling to other engine parts. As you drive your car, the temperatures on your engine rise, making the valve cover gasket wear out with time. A worn-out valve cover gasket allows the oil to drip to your spark plugs. 

b. Failing O-Ring Seals

If you look at the bottom of the spark plug, you will see some O-ring seals. If the O-ring seals fail, the oil leaks into your spark plug wells. 

You should not ignore the issue; instead, you should replace the O-ring seal immediately.

c. Failing Piston Comprehension Rings

At the bottom and top of the car engine piston, there are some comprehension rings. If the cylinder wall gets excess oil, the comprehension rings help in scrapping it off. They also ensure that oil does not get into the combustion chamber. Unfortunately, once the comprehension rings fail, the oil leaks into your spark plug well. You can quickly tell if your comprehension rings are failing if you notice a blue exhaust that smells oily. 

d. Failing Pistons

If you hear some rattle and knocking noises when the car is running, that’s an indication of a failing piston. It occurs due to excessive heat, causing it to develop either a hole or a crank. Once the piston fails, it results in engine misfiring, loss of power, and also excessive oil burning. You should take it seriously and repair it immediately.

e. Worn Valve Guides

When the engine is working, it requires a valve guide to regulate air intake. With time the valve guide gets worn out, leading to serious engine problems. Some of the symptoms that it has worn out include; the blue smoke. You will also notice ash or oil in your spark plug oil. If you notice any of these symptoms, take it to the mechanic to have it repaired or replaced immediately. 

Once you notice all these oil-fouled spark plugs symptoms, you should not ignore them. Get the mechanic to inspect and repair it immediately. 

A Quick Way to Fix The Problem

You need to read the car manual to understand repair procedures. Get the right tools and parts before attempting any repair. Some of the tools you require include pliers, screwdriver, ratchet, and extension. You also need the power handle, O-ring spark plug seal, the valve cover gasket, socket, spark plug socket, and the engine sealer. For the oil, have a spray cleaner

I. Analyze the Gasket Position

The work of the gasket is to seal and prevent leakage. Gasket size and shape depend on your car component. If the gasket gets damaged, it allows the oil to spill over to the spark plugs. That’s why you need not only to check the position of the gasket but also it’s status. 

II. Remove both the Valve Cover and Even the Spark Plug

Remove the spark plug and the valve cover.

III. Seal Removal

The primary cause of the oil on your spark plug thread is the seals. You can find them on your spark plugs. You should not remove either the seals or the gasket if you don’t have a new one with you.

IV. Install Your New Valve Cover Gasket

Ensure the gasket resembles the shape of your component. Before buying it, ensure it has the right material and also the right quality. When installing the new gasket, add a sealer (A liquid that prevents the gasket from slipping over.) The liquid also makes it remain tightly secured, preventing oil leakage to the spark plug. 

V. Install Your Spark Plug Gasket

On top of the spark plugs well, there is a rim where you need to place your spark plug casket. Bolt the nut well and in the right order to prevent valve cover damage. After putting all the parts back to their original position, use an oil cleaner to rinse any part that the oil has spilled over. Keep on checking your car to ensure that no oil spills your spark plug threads.


As a car owner, you have the responsibility of ensuring that your car remains in the right condition. If the vehicle starts showing some weird symptoms such as decreased engine performance, back-fire, poor fuel economy, gas smell, among other symptoms, have it inspected and repaired.

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