While Oil is a crucial part of an engine, it can still do a lot of harm if it starts leaking somewhere in the body. If you find oil on the spark plug thread during a routine checkup, ignoring it might not be the best idea.

In this article, we’ll discuss how you can deal with oil on spark plug threads, its causes, and how you can figure it out without a routine checkup.

What Causes Oil on Spark Plug Threads?

1. Damaged Valve Cover 

The valve cover is a piece of plastic covering the engine’s intake valves. The intake valves allow air into the combustion chamber where fuel is injected. Replace it if it is broken or old since this might cause oil gathering on your spark plug.

2. Broken Piston Rings 

Broken Piston Rings 
Credits: TuningBlog

Piston rings seal the top of the piston inside the cylinder. Over time, the rings wear down and need to be replaced. The engine will leak gas and oil if the rings do not fit properly. 

3. Leaking O-ring Seals

Credits: Youtube

They are used to prevent oil leakage and protect mechanical components. In addition to sealing, these types of seals are designed to withstand high pressures, temperatures, and vibration. The oil travels through the manifold to the spark plug threads. 

4. Improper Cleaning 

Improper cleaning methods can leave debris behind on the spark plug. This debris can then become trapped between the gap of the spark plug, causing the spark not to fire correctly. 

5. Ignition System Problems 

Incorrect ignition timing can result in excess oil buildup on spark plugs, leading to problems with the engine. Also, excessive heat causes oil to build up on spark plugs. If left untreated, this buildup may cause damage to the engine. 

Other Factors That Can Affect the Life of Your Spark Plug

1. Old Spark Plugs 

Old spark plugs have worn out and lost their insulating material. The metal shell of the plug becomes exposed, which increases its conductivity. This makes it easier for current to flow through the metal shell and cause sparks. 

2. Water 

Water can enter the spark plug’s internal chamber and collect in the gap between the center (or firing) electrode and the ground electrode. This water can corrode the metal parts of the spark plug and reduce its insulation. Water itself is bad, whether it is in spark plugs or water in engine oil.

3. Poor Maintenance 

Grime and dirt can clog the air filter, preventing clean air from entering the engine. Dirt also gets trapped in the gaps between the center and ground electrode, reducing the amount of voltage that reaches the spark plug’s firing tip. If you don’t change your spark plugs often enough, you could end up with dirty spark plugs. 

Symptoms Of Oil on Spark Plugs 

Inspect your vehicle’s spark plug every year. If a layer of carbon or oil is on it, repair or replace it. You need to change or fix your spark plugs if you notice these symptoms. 

  • You have bad gas mileage. 
  • You have low oil pressure. 
  • Your engine is facing performance issues. 
  • There is excessive smoke coming out of the exhaust pipe. 
  • Your engine stops without warning. 
  • When you accelerate, the engine makes a loud rumbling noise. 

You have difficulty getting the engine started after sitting idle for a long time. 

Suppose your car shows any of the symptoms above regularly. Set up a visit with your technician to get your spark plug checked and repaired. Keep reading if you intend to fix your spark plug yourself. 

What Are the Consequences of Oil on a Spark Plug? 

  1. If the spark plug fails while the engine runs, the engine will overheat and catch fire. 
  2. It can affect your vehicle’s range and fuel economy. 
  3. Over time, oil buildup can wear down parts of the engine. 
  4. Oil on a spark plug can reduce the amount of power the engine produces. 

How Do You Remove Oil on Spark Plug Threads? 

Whether you want to fix your spark plug yourself or simply want your car to drive a couple of extra miles so you can get to the mechanic.   

Here are three options for you to consider that can help you remove oil from your spark plug: 

1. Wire brush

wire brush cleaning spark plug

This is the easiest method for removing oil from a spark plug. Make sure to wear gloves while doing this, as the oil can get into your hands and transfer to the spark plugs.  


  1. First, fix your spark plug properly onto something. Make Use of a stand or a holder. 
  2. Make sure to rub the brush over the spark plug thoroughly. Continue until the spark plug is shiny and clean. 
  3. Wipe down the threads with a small amount of alcohol. 
  4. Apply some type of sealant to prevent future oil buildup, e.g., silicone, graphite, etc. 

2. Sandpaper


Using sandpaper is another inexpensive method of eliminating oil from your spark plug.  


  1. Wash the spark plug in alcohol or gasoline. 
  2. Rub a brush gently over the plug to remove any carbon. 
  3. Rub the spark plug with sandpaper, and clean the tip of the plug thoroughly because that is where the spark occurs. 
  4. Continue until the spark plug is shiny and clean. 

3. Heat 

Heating your spark plug to a specific temperature can significantly aid in the removal of an oil or carbon layer. The oil on your spark plugs is burned and melted by heat. To avoid any danger, wear a mask and gloves. Also, don’t leave it on a high flame for too long, or it will melt the plug. 


  1. Place your plug with a holder on top of your gas stove. 
  2. Heat it for 5-10 minutes on a low-medium flame. 
  3. Wait for it to cool before reinstalling it. 

If these methods above don’t work for you, here’s a quick video below that will help you clean your spark plugs properly.

How Can You Avoid Oil on Spark Plug Threads? 

1. Getting consistent service 

This is the best way to get your vehicle in the best possible condition. You should also contact your mechanic and inform them of the problem you’ve faced, as this can prevent further damage. Regular vehicle maintenance can protect you from engine damage and poor performance caused by the oil on the spark plug.  

2. Using Oil-Free Lubricants 

Next, you must make sure you are using lubricants free of oils. Oil can cause buildup and clog the threads of the spark plugs. Your best bet is to use a synthetic oil-based lubricant, such as WD40 or a similar product. These products are designed specifically for cleaning and lubricating parts that require extreme conditions. 

3. Using Good Quality Spark Plugs 

Finally, if you still have problems with your spark plugs, you should consider replacing them. A good quality spark plug will last longer than a cheap one and provide you with many years of service. 


In conclusion, oil on the spark plug might adversely harm your engine’s performance and lifespan.  We should serve our cars after regular intervals and take precautions to prevent oil from accumulating around the threads of the spark plugs. Also, use high-quality spark plugs to avoid significant harm to your car.

FAQ’s on Oil on Spark Plugs

Is it normal to have oil on spark plug threads?

Oil on spark plugs is not normal. Oil-covered spark plugs can cause serious damage. If they get dirty, you may need to clean them before putting them back in the engine.

Can a bad PCV valve cause oil on spark plugs?

A bad PCV valve can cause oil on spark plugs. If the engine is running fine and suddenly stops working, check the PCV valve first. You may have a leaky valve causing oil to collect around the spark plug thread.

Can an oil leak cause a misfire?

An oil leak can cause a misfire. When an engine starts, the spark plugs are ignited. If they don’t ignite properly, then the engine won’t start. A leaking oil line could cause the spark plug not to fire.

Will oil on spark plugs cause the car not to start?

Oil on spark plugs causes carbon buildup inside the combustion chamber. Carbon buildup reduces the amount of oxygen reaching the engine’s cylinders. The spark plug will no longer fire properly if the oil is allowed to dry out. When the spark plug does not fire correctly, the engine will not start.

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