5 Causes of Oil Leaking Into Spark Plug Wells

Finding oil in your spark plug wells is alarming, but try not to stress too much (but do take it seriously). Oil leaks happen, and the oil is not always going to makes its way down to your driveway or garage floor.

In this article, we’ll look at the most common reasons you’re seeing oil accumulating inside your spark plug wells and how you can correctly determine the root cause. The fix may not be as bad (or expensive) as you may think.

Top 5 Reasons Oil Leaks Into a Spark Plug Hole

Later, we’ll touch a bit on the symptoms you may experience to lead you to the conclusion that there’s oil in the spark plug chamber, but first, let’s look at the most common causes of engine oil getting into a spark plug hole.

1) Worn Valve Cover Gasket

valve cover gasket leak

The engine has a metal part on top of it called a valve cover. A valve cover gasket sits between this cover and the top of the engine cylinder head. This keeps the engine sealed so that oil does not leak from it.

However, all the heat from the engine will wear down the valve cover gasket as time goes on. It will eventually start to crack and become hard or brittle, which then allows oil to leak through the gasket.

You can simply replace the leaking valve cover gasket if you catch the problem fast enough. Otherwise, your engine may suffer permanent damage due to insufficient oil.

2) Old Valve Guide Seals

bad valve guide seals

Vehicles depend on valve guides to assist in managing the intake of air into the engine. Basically, the valve guides secure the valves during the operation of the engine. The only problem is that valve guide seals eventually start to wear out as you continue using your vehicle.

At some point, you will likely need to replace them because bad valve guide seals will not be able to prevent oil from leaking into the spark plugs. Once that happens, you could have a lot of problems with your engine that will cost thousands of dollars to repair.

3) Bad O-Rings

spark plug well seals

Under the spark plug tubes, there are O-ring seals. Once an O-ring becomes worn out or damaged, oil will leak through and make its way to the spark plug tube. You’ll need to fix this problem quickly before the engine is affected too much.

And since the oil saturates the spark plugs, you’ll need to replace the spark plugs as well.

4) Bad Piston

damaged piston

A piston can crack if it gets exposed to too much heat. Then it will start to make knocking sounds and rattle quite a bit. More important, a bad piston will let oil leak into the spark plugs and that will create all kinds of problems.

Your engine will misfire frequently, and you’ll experience a weaker engine performance. These are all things that will ruin your engine if the piston is not replaced promptly.

5) Bad Piston Rings

bad piston ring symptoms

Piston rings exist on the top and bottom of the pistons of an internal combustion engine. The purpose of the compression rings is to stop oil from entering the combustion chamber and to remove extra oil that gets onto the cylinder walls.

However, if you have worn out piston rings, then they won’t be able to stop oil from flowing toward the spark plugs. You’ll also see blue exhaust and there may be a smell of engine oil that consumes the cabin.

Signs That Oil Leaking Into Spark Plug Wells

When oil leaks into your spark plug wells, you’ll likely notice several symptoms that indicate an issue. Keep an eye out for the following signs, which could be caused by oil finding its way into your spark plug wells:

Misfires and Engine Problems

Misfires are a common symptom of all sorts of engine issues and oil in your spark plug wells is one of them. This oil can interfere with the spark plug’s ability to ignite the air-fuel mixture, leading to incomplete combustion and engine misfires.

Blue Smoke

Notice blue smoke coming from your exhaust? This happens because the excess oil is being burned off along with the fuel. When you see this smoke, it’s time to investigate further and fix the issue.

Increased Fuel Consumption

When oil affects your spark plugs, it can throw off the air-fuel mixture in your engine. This can lead to your vehicle burning more fuel than it should, resulting in reduced fuel economy and potentially harming your gas mileage.

Engine Backfiring

Oil in the spark plug holes can also cause your engine to backfire. When this happens, you might notice a loud popping noise and a jolt when you’re accelerating or decelerating. This can be quite alarming (and annoying), but fixing the oil leak should help alleviate this problem.

Gas Smell

If you notice a strong gas smell coming from your engine or exhaust, this can be a sign that oil is leaking into your spark plug chambers. The improper air-fuel mixture can lead to excess gasoline being present in the exhaust, giving off a noticeable odor.

Identifying the Leak Source

If you discover engine oil in your spark plug wells, pinpointing the origin of the leak is the most important thing to address the problem.

Start by inspecting the valve cover gasket – cracked or brittle gaskets are a common culprit as heat and age degrade the seal. Valve guide seals are another likely source, especially if they haven’t been replaced in some time. As seals wear out, oil can slip past into the cylinders.

Also examine the piston rings – worn rings fail to contain oil, allowing it to drip into the combustion chamber. Cracked or damaged pistons themselves may also leak if exposed to excessive heat.

Finally, look for compromised o-rings under the spark plug tubes that could permit oil to seep through.

Thoroughly checking these common problem areas and components can help accurately identify the root cause of an oil leak into spark plug wells. Focusing repair efforts on the specific point of leakage, rather than symptom management, provides a lasting solution.


12 thoughts on “5 Causes of Oil Leaking Into Spark Plug Wells”

  1. Please help I have an old Hyundai Accent 1.3, 96, recently it has been smoking badly, producing light blue smoke, and about very that spark plugs barely last a week , they get oily and engine starts misfiring and underperforming. What may the possible cause

  2. Any dealership used or new has its reputation and public option more so customer satisfaction is and always will be the make or break factor in the “sales world”
    You buy a car from a dealership you better get 3 months worry free usage out of that car. 500$ car or a 50000$ car 3 months or that dealers” name is mud”
    In other words. . Take it back asap if u don’t your a fool and If they don’t provide u with a different car or money back they are not going to be in business for long.
    Thx to google …haha

  3. My 2011 chevy traverse had oil in the back plugs and look like oil in my brake fluid as well but I dont know what’s causing it

  4. Hello,

    Please help. I just bought a Audi Q3 2.0 TFSI Automatic 125000 Kms from a dealer. Very next day car suddenly started shaking and engine light on. I called road side assistance and they found Spark plug is fouling and misfire in cylinder 2. Also the spark plug #2 had lots of oils (thread side). Next day I got my car checked and car mechanic said everything seems good and there is no leakage (gaskets , valves etc). He assumed while last servicing some one over filled the engine oil. He cleaned the plugs and extra oil in chamber.

    After few days, same problem again and cylinder 2 misfire and spark plug fouling with oil. This time spark plugs (all 4 ) were changed and car was running good. But now engine seems very rough so I got the car checked again, from Audi this time. They said car engine is rough and Misfiring also error code P2188 showing and oil on spark plug#2.

    They said there is no external leakage from engine and might be something internally leaking. But they need to perform some oil consumption and compression test and those are expensive and if there is problem with piston or piston rings and it’s very serious and very expensive to fix.

    I just bought the car from dealer and very next day car started the problem. Dealer said they have inspected the car and also car was inspected form independent car inspection company and nothing wrong with the car.

    Please help and suggest what action do I need to take. Do I need to return the car to dealer if he is not agree then take legal actions or Do i need to spend more money for the engine tests.


    • I am not a lawyer, so I can’t tell you what legal actions you can or should take (especially since they vary so much by location). It is up to you if you wish to try to return the car to the dealer or run a compression test to figure out what’s wrong with the engine.

    • Hello I had my plugs replaced in my 2014 ram 1500. Now its misfiring and found one of the coil packs is bad and also seem to have one plug out of that pack that has oil on it idk why. It just all started after the tune up

      • See if you can figure out where the oil is coming from. I would guess your valve cover gasket is leaking.

        How did you determine one of the coil packs is bad?

  5. I found that everyone I have spoken to in person that has a Toyota Camry (most commonly being this 94 2.2 4 cylinder) {yes, even still. LOL} has had the same problem, as well as many others. Thus the most common we know of is from the oil fill cap being in line and right next to the spark plugs. So oil constantly get to the plugs.

    Even when covering the area, if the wind blows just right, it will seep down to the spark plugs. Now whether this is an older car issue or something more common for those kind I’m not sure? Can not find anything this specific online.

    Do not have anyone to speak to about this issue now. Everyone seems to address all the other problems and solutions which one starts to dismantle the motor. I’m not really sure if taking the valve cover gasket off is necessary? Exactly how should I clean it and what to do now?

    One time it was misfiring and my ‘previous’ mechanic (Great, honest, fair & rare. Unfortunaly battling C! Thus on no bother) pulled the wire up a little bit so it almost stopped. Said will run on 3 cylinders until could get new plug and wire. Not one to run car hard anyway. Still, week later it stoped. Pushed back in and twas fine.

    I try to sop up the oil as quick as possible if spills. It seems like times I have spilt more and nothing has happened. Yet a bit and it starts to misfire again. Only as it sit still at lights. More so on damp days.

    I have replaced a plug and it was fine. Another plug another time, and it was NOT fine. So then suggested that I should replace the wires that I had just got a month before. Spent $80 on that new set. Cannot figure if a way to just test them? So i can replace just one if needed?

    Trying to be thorough and analyze every angle. Really cannot afford to take this to some shop. Only ever get expensive solutions. Most times unneeded, as if i was just a dumb girl.

    I have been disabled, so more limited now. Most of my dads tools were stolen from me. Still doing best i can. No way can i replace everything every time. Desperately need the vehicle but I’m afraid of causing further damage.

    I only must drive it a couple miles a day and sit through those couple lights. But how long can I do that, if at all now? If anyone can help me i would greatly appreciate it. Any and all good advice is desperately needed. Thank you so very much. Take care all! Jennifer

    • Hello Jennifer, I’m not one too comment on these websites, but I hope I can help (if you still have the issue) the way you can test a bad coil is disconnecting the cable that it is connected too. If the coil is bad the engine will not change, it will run the same. The idle will not go up or down. If you do the same on a working coil the idle will drop and rise due too the engine trying to compensate for the loss of 1 cyilinder. Try changing the faulty coil too see if that fixes the issues. Now with the oil leak I am unable to tell due too I am not too familiar with Toyota Camrys, hope I helped, happy Hoildays, and happy new year!


Leave a Comment