There Is Oil on My Spark Plugs: Causes, Symptoms, and Repair

So, you pop the hood, and what do you see — oil on your spark plugs. What now?

Before you start throwing money at your mechanic, consider this. What if you learned how to clean and fix oil on spark plugs all by yourself? If you learn how to do it yourself, you’ll save a lot of time and money in the future.

If you want to see how to fix this problem yourself and stop it from ever happening again — you’ve come to the right place.

What are the reasons for oil on spark plugs and hot to fix the problem.

Why Is There Oil on Your Spark Plugs?

If you want to fix the problem yourself, which I encourage you to do, you need to find out why this is happening.

These are the five common causes for oil on spark plugs:

Leaking Valve Cover Gasket

Obviously, we’re first going to talk about the most common reason why you could be seeing oil on your spark plugs. In case you didn’t know, a valve cover is a metal part which is located at the top of the engine. It helps seal the engine and prevents oil leaks.

Since they’re usually made out of rubber or silicone, they can wear out due to heat, age or oil erosion. Once that happens, they can leak out into spark plug wells. While this isn’t always a costly repair, you do need to react fast if you want to avoid an engine overhaul.

Leaking O-Ring Seal

You’ll find O-ring seals at the bottom of the spark plug well. If you have a defective O-ring seal, it will let the oil pass through the valve and end up on your spark plug. A leaking O-ring will cause your engine to backfire.

Replacing a leaking O-ring seal is similar to replacing a valve cover. It won’t cost you much, but you should do it as soon as possible to avoid permanently damaging your engine.

Worn Out Valve Guides

Valve guides regulate the air intake in your engine. The intake and exhaust valves are timed to slide up and down. In essence, they allow the air to enter the combustion chamber and exit through the tailpipe.

If your valve guides stop working, oil can enter the combustion chamber and cause serious damage to your engine. So, if you see blue smoke coming out of your tailpipe, you should replace your valve guides immediately.

Broken Piston

If the piston gets too hot, it might crack or break. The three most common symptoms of a failing piston are:

  1. Rattling noise when your car is running
  2. Excessive oil burning combined with a loss of engine power
  3. Engine misfiring

A broken piston can cause the oil to seep into your combustion chamber. Again, if you have a broken piston, you need to get it fixed as soon as possible to avoid an engine overhaul. Not only can a broken piston permanently damage your car, but the more you wait, the more expensive the repair will be.

Broken Piston Compression Rings

Next, let’s talk about broken piston compression rings. Each piston has a set of two rings that surround it. The combustion rings seal off the combustion chamber and stop the oil from seeping into it. Not only that, but they also help scrape off or “wash” any oil that has built up on the sides of your combustion chamber.

If one, or both of these rings fail for some reason, you will most likely see oil on your spark plugs. Moreover, if there’s a gas smell coming from your tailpipe, you should consider changing your compression rings.

Symptoms That Show You Have Oil on Your Spark Plugs

Let’s talk about the five most common symptoms you may encounter if you have oil on your spark plugs.

A Gas Smell Coming from the Exhaust Pipe

When you smell a combination of oil and gasoline coming from your tailpipe, you should check your spark plugs. Also, this is a sign that you should check your piston compression rings, as that’s what’s most likely causing the problem.


If your spark plugs aren’t working the way they should be, neither will the combustion chamber. The fuel particles will enter your exhaust pipe with a high-energy charge, causing a backfire.

Blue Smoke Coming from the Tailpipe

If there’s blue smoke coming from your tailpipe, you need to see a mechanic as soon as possible. Blue smoke usually means your engine is in critical condition and you need to replace your valve guides.

Poor Engine Performance

Since you have a reduced combustion efficiency, expect a decrease in your engine’s performance.

Poor Fuel Economy

Along with a slow-working engine, you’ll also have a higher fuel consumption because your combustion is less efficient.

Slow Acceleration

Do you have to put your pedal to the floor to get some speed? A new spark plug could probably help you remedy this problem.

Trouble Starting Your Car

Not being able to start your car can mean a lot of different things have gone wrong, not only your spark plugs. However, if you want to diagnose the problem yourself, you can save some money and time by buying a good car monitoring system.

Diagnosing the Problem

If you want to make sure that oil on your spark plugs is what’s causing the problem, and not something else — you need to learn how to make a diagnosis.

Visual Inspection

Check to see if there is any oil coming from the valve cover gaskets. If you see any oil, the valve cover needs to be replaced immediately.

Also, you should check the exterior condition of the spark plugs. In case you see any oil on the coil-over-plug, spark plug wires or the ceramic coating, you need to replace your O-ring seals.

Engine Tests

There are two engine tests you can do to rule out the valve gasket or O-ring as the culprits of your problem. You can perform the engine compression and the engine differential pressure test. While the latter is much more precise compared to the former, it’s also much harder to do.

If you want to learn how to do an engine compression test, you can follow this link. However, if you have the knowledge and the equipment to do a pressure test, and just need a reminder, watch video below to see how it’s done.

How to Repair Oil on Spark Plugs

Before you start, you’ll need to gather all of these items:

  • Screwdriver
  • Pliers
  • Power handle
  • Engine sealer
  • Valve cover gasket
  • O-ring spark plug tube seal
  • Spark plug socket
  • Spray cleaner for oil
  • Ratchet and extension

Here’s a step-by-step guide on how to fix oil on your spark plugs:

1. Disconnect the Battery

In order to replace the gasket valve and the O-ring, you first need to disconnect the battery. Also, if the wiring harness is in the way, you need to remove that as well.

2. Unscrew the Valve Gasket Cover

Once you’ve disconnected the battery, you should unscrew the valve cover. You can use a screwdriver to pry it open. Next, remove the spark plugs and tubes. By doing so, you will be exposing all of the seals and gaskets that need to be replaced.

Valve gaskets and O-rings are pretty inexpensive, and you can find them in online stores like Amazon. Also, before putting in the new gasket, you should apply some sealant. By applying a sealant, you’ll ensure that the gasket doesn’t leak anymore.

3. Replace the Old with the New

Now that you’ve taken out all of the old, defective parts, you need to install the new ones and secure the screws in place. If you’ve never done anything like this before, watch the video that is linked below.

Of course, if you aren’t confident in your skills as a mechanic, you can always go to a professional. They will replace your valve gasket and properly seal in everything.

How to Stop Oil From Getting on Spark Plugs

Keep in mind that valve gasket covers or O-ring seals weren’t made to last forever. Over time, they will wear out and you will have to replace them at some point. With that being said, the more you take care of your car now, the less often you’ll have to worry about this problem happening again.

Also, if this is the first time you found oil on your spark plugs, you might want to go to professional. However, don’t just leave your car there and go for a coffee somewhere while the mechanic does all the work. Ask the mechanic if you can stay there, watch what they do, and ask questions. By seeing how it’s done, you can learn how to do it yourself.

Of course, if the mechanic says no, you can always resort to watching YouTube tutorials online. What’s more, once you learn how to do it yourself, you’ll save so much time and money. The final advice I have to give you is to try and learn more about your car. By taking preventive measures, you’ll be able to avoid getting oil on your spark plugs again.

Final Thoughts

Just because you found some oil your spark plugs doesn’t mean you’ll have to overhaul your entire engine. It just means you’ll have to be more careful in the future and pop your hood more often to check for the signs.

As soon as you see oil on your spark plugs, perform the tests and see what’s causing the problem. Once you’ve figured that out, take immediate action and fix everything that’s broken. The good news is that fixing the problem won’t cost you that much, especially once you figure out how to do it by yourself.




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