Oil in the Spark Plug Well – Causes and DIY Fix

Spark plugs are usually the first thing checked when an engine suddenly misfires or fails to start. If you have oil in the spark plug well, it could damage the spark plugs and prevent them from firing at all. You will need to replace them.

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To prevent this from happening, we need to find out where the leak is coming from.

What Causes Oil in The Spark Plug Well

Every time there is a leak, the obvious culprit is the gaskets. The primary purpose of gaskets is to prevent the escape of gases and liquids from one section of a vehicle to another. Gaskets deteriorate over time and can be damaged by improper installation, overheating, or the high pressure that is produced inside a cylinder during compression.


When the valve cover gasket deteriorates, it will start to harden and crack. A leaking valve cover gasket will cause the oil in the spark plug well, so you have to replace it. Over-tightening bolts will not stop bad gaskets from leaking.

On most types of engine designs, the gasket comes as a kit. A rubber seal that seals the outside of the cover with separate O-rings that seal the individual spark plug wells in the center.

See the picture below:

How to Remove Oil from Spark Plug Well

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Once your spark plugs are soiled with oil, it’s best to change your spark plugs. But before you do this, you should first remove all the oil in the spark plug well.


  1. First, spray the spark plugs wells free of debris before pulling the spark plugs. You don’t want any of that road grime getting into your engine.
  2. Remove all the spark plugs.
  3. Turn the engine over for a few seconds with a rag over the spark plug holes. Caution: The oil may go all over the place so jam it in there and twisted it around.
  4. Without the plugs in it will turn over pretty fast. Oil and any dust will be forced out of the hole.
  5. Change the spark plugs.

How to Replace Valve Cover Gasket Kit

Now proceed with replacing the valve cover gasket.

  1. Tap the valve cover gasket with a rubber mallet to loosen its grip.
  2. Remove the old valve cover gasket and the spark plug O-rings and install the new one.
  3. Apply silicone only if it is needed.
  4. Tighten valve cover to the recommended torque. Valve cover bolts don’t require too much torque.

As mentioned earlier, a valve cover gasket is sold as a kit spark plug o rings, rubber seal, and sometimes a coil cover gasket.

Related: What Happens if You Drive a Car Without Oil? Expect Critical Damage

Symptoms of Oil in the Spark Plug Well

If the oil leaks into the spark plug wells, it will drastically affect the engine’s performance. The most common symptoms are engine misfires, increased oil consumption, and blue exhaust. Sometimes the car won’t start.

  1. Engine misfire – A sudden engine misfire may be caused by improper spark plug installation or premature ignition of the fuel. Oil in the spark plugs causes this. Ignition can not take place because oil has taken the place of the gap between the center electrode and ground electrode in each cylinder.
  2. Increased oil consumption – Oil may escape through a leaking valve cover gasket or an unsealed valve stem seal. You may notice that your oil level is low after a short period of use.
  3. Blue smoke – Oil in the combustion chamber will prevent the normal air-fuel mixture from completely burning and leaving a lot of unburned hydrocarbons, carbon monoxide, and carbon dioxide which quickly turn to blue smoke. The result is poor performance and high fuel consumption.
  4. Car won’t start – If the oil is on the spark plugs instead of inside the engine, it will cause your car not to start. The reason is that air and oil do not mix well. So when the computer tries to ignite, oxygen reaches only a small part of each cylinder. The remaining oil will accumulate between the coil’s electrodes and prevent the ignition from taking place.

Read more: Clean vs Dirty Engine Oil Comparison


Spark plugs are essential for gasoline-powered vehicles, as they help to ignite the engine. Oil in the plug well can be problematic because this may cause misfires, engine failure, or other problems. Thus, you should know how to remove oil from the spark plug well and replace a valve cover gasket if needed.

Replacing valve cover gasket and spark plug o-rings are very easy and don’t require any special tools. If you have a problem with oil in the plug wells, replace it and clean your plugs to avoid misfires. The best way to do this is to change your plugs as well as gaskets at the same time.

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