Car Issues and Fixes

Oil on the Spark Plugs – Causes and Fixes 

Avatar Adie Tinkle -

Spark plugs are crucial components of every vehicle as they generate the spark that ignites the fuel and air mixture in the internal combustion chamber. Spark plugs can tell a lot about the health of your vehicle’s engine. Finding oil on the spark plugs can indicate a fault with the ignition system. The plugs can also be carbon fouled, indicating a rich running condition. 

A common observation during spark plug inspection is oil saturating an electrode tip. Oil plays a significant role in lubricating the engine’s components while operating. If the components do not have enough oil, the engine will overheat because of the friction caused by moving components rubbing against each other. 

However, oil pouring into the spark plug is also undesirable. It can cause issues with your engine’s functioning and performance. Oil leaking into the spark plug must be checked promptly to maintain car service. 

How Does Oil Get on Spark Plugs?

An important question you might ask is how oil gets on your spark plug. A likely explanation for why there might be oil on the spark plugs is because of an unbalanced mixture of oil. Usually, the ratio is 50 parts gasoline and 1 part oil. The disruption in this ratio can cause spark plugs to be drenched in oil. 

Faulty piston rings cause oil to seep through your spark plugs. You can visibly see the presence of oil on the sparkplug and any visible leaks. You can also check the oil layer below the second ring. This way, you can identify a leak from piston rings. 

Warning Signs of Oil Filling on Spark Plugs

It would be best to stop the leak as soon as you can. There are always warning signs of oil filling on the spark plugs. 

  • The engine is Low on Oil

You might find that you need to fill up with oil more frequently.

  • Burning Oil Smell: 

You can easily track the smell of oil to its source and get your spark plugs cleaned. 

  • Engine Misfire or Running Roughly 

Misfires or backfires are sounds that can sometimes be mistaken for gunshots; they can happen when the engine has too much or too little oil. 

  • Overheating Engine 

White smoke can appear from the bonnet if the engine is overheated. The smoke indicates that the engine is burning so hot that it is evaporating water.

  • Valve Cover Dirty or Leaking 

If the valve cover is dirty, you will have to clean it, and if the valve cover is leaking, you will need to replace it, as keeping it can be dangerous. 

Causes for Oil Leaking on Spark Plugs 

There are many potential causes for spark plug contamination, some being more dangerous than others. Here are some of the most common causes of spark plug oil contamination 

  • Compromised Plug Well Grommets 

Specialized grommets can be found on various engines, the role of which is to prevent oil from seeping into the plug well. However, these grommets can face aging and heat distortion, thereby providing reduced protection over time. 

  • Leaking Valve Cover Gasket 

The valve cover is a metal piece on the engine. A valve cover gasket is between it and the cylinder head.

This engine seal prevents oil leakage. However, over time, the heat from the engine warms down the valve cover gasket. If the valve cover gasket is compromised, the oil will leach from beneath the engine’s valve cover and seep into the void or well.  If you identify this issue early, resolve it by replacing the leaky gas cover gasket. Otherwise, your engine can face permanent damage for not receiving the required fuel. 

  • Faulty O-Rings 

O–ring seals are present beneath the spark plug tubes. The oil seeps through the O–ring if it is cracked or worn out and reaches the spark plug tube. It is important to address these issues promptly, as not doing so can cause permanent damage to your engine. Also, change the spark plugs if they are saturated with oil. 

  • Faulty Piston: 

If the piston is subjected to too much heat, it can crack. It can also begin to produce a lot of noise and rattling. A malfunctioning piston can cause oil to leak into spark plugs, leading to various issues. 

It can also lead to regular misfires and poor vehicle performance. These factors can cause your engine to fail if the piston is not changed as soon as possible. 

  • Faulty Piston Rings

An internal combustion engine’s pistons have piston rings on the top and the bottom. The role of compression rings is to prevent the oil from entering the combustion chamber and to remove extra oil from the cylinder walls. If the piston rings are worn out, they will not be able to prevent oil from flowing into the spark plugs. You can also observe blue exhaust and a smell of engine oil that permeates the interior. 

  • Faulty Turbocharge 

Turbocharge is also a part of the engine that can leak onto a sparkplug. This leak can sip from the combustion chamber within the turbocharge and onto the spark plugs. You can check the intercooler intake pipe. If it is filled with oil, it means that turbocharged is the culprit. 

How Can Oil on Spark Plugs Affect Your Engine and Vehicle?

In a normal situation, only air and fuel should come in contact with your spark plugs, and there shouldn’t be any oil on your spark plugs. If the oil reaches the spark plugs, an oil-soaked spark will not be able to function effectively. It will lead to no combustion, no ignition, and no energy generation. Even if the fuel pump is supplying fuel to the chamber, the fuel might be able to escape the cylinder without burning. 

An oily spark plug can affect the engine’s performance, and if left untreated, it can cause permanent damage, causing too much fuel to be pilled up in the oil pan. 

It might not seem like a big problem, but it can have multiple effects on your vehicle. Therefore, it is important to resolve this issue immediately. 

Side Effects of Oil on the Spark Plugs

Here are some side effects of oil leaking into spark plugs: 

  • Reduced Engine Performance and Fuel Efficiency. 

Even the slightest deviation in the function of a single component can affect your engine’s efficiency. When the spark plug does not make sparks effectively, your engine suffers, and as a result, you will have to deal with reduced performance and efficiency.

  • The Gas Smell from the Exhaust Pipe 

There are many problems that can lead to higher fuel consumption. However, if you smell gas from your car cabinet, the culprit might be oily spark plugs. It can happen when a mixture of gas and oil comes from the tailpipe. It can cause noticeable gas smell.  

  • Engine Misfire

A misfire happens when the engine momentarily hesitates, stumbles, or loses power while accelerating. Other causes of misfires include idling engines, which can cause a rough or uneven idle. The engine misfire can repeat randomly or under specific operating conditions. 

Though there are many other reasons behind this issue, oil in the spark plug is quite prominent. An engine misfire can happen if components such as oxygen, fuel, or spark plug aren’t working in the right order or at a precise time. 

  • Engine backfires

An engine backfire occurs when the fuel is ignited at the wrong time. The presence of oil on spark plug threads causes the engine to backfire. 

An oily spark plug might not be able to make a spark at a precise moment, causing the exhaust valves to be open. 

Because the fuel particles are not ignited properly, the unburned fuel escapes from the cylinder to the exhaust system with force. This misfired spark plug ignites the rich air-fuel mixture, causing a small explosion or a loud band sound in the tailpipe. 

How to Fix Oil on Spark Plugs 

Oil leaking into spark plugs can be caused by numerous issues, as described above. Therefore, it is important to fix these issues. For that, you need tools, including. 

  • Spray Cleaner 
  • Power Handle 
  • Screwdriver 
  • Socket and spark plug socket 
  • Ratchet and extension 

Oily Spark Plugs – Guide to Fix the Issue 

Now that you are aware of the causes behind oily spark plugs, it is time to fix them. Here is a step-by-step guide on how to fix the oil on a spark plug. Make sure to turn off your vehicle and disconnect its battery terminals. This will ensure that the engine is off and not supplying power. 

The first step is to examine the head gasket. It is a plastic band meant to seal. You need to remove the valve cover with a screwdriver to inspect it. After doing that, you can see the spark plug and the tubes. The seal and gasket will also be removed, and you can inspect any damage and cracks. 

If you find the head gasket to be the cause of oil on spark plug threads, you will need to replace it immediately. 

Removal of Spark Plugs 

Because spark plugs are present in the valve cover, so to replace them, you will also have to replace the valve cover. Before this, it is important to take out the spark plug tubes and put them on the sides. 

The next step is to remove the clamps from the valve cover hoses using pliers. Remove the hose with your hands. Then remove the wiring harness on the top valve cover. After doing that, remove the nuts from the valve cover using the power handle and socket. Removing the valve cover allows you to remove the seals present in each spark plug. 

It is preferable not to use the old plugs again after cleaning them. Some of the oil might be left on them, which can waste all your effort. The best thing is to replace them with new sets. 

Clean the Head and Valve Cover 

Clean the head and valve cover before installing the new gasket and seals. It will allow you to remove old particles, and the new part installed will have a tighter seal. 

To prevent cylinder head and cylinder head from damaging, use the right grease and only use plastic equipment. 

New Valve Cover Gasket 

It is essential to get the gasket in the right shape. It is also important for you to check the material and quality of the gasket before purchasing it for the vehicle. Normally, high-quality silicone material is used. After getting it, the next step is to add a liquid called sealer at the edges so the new gasket doesn’t slip over. 

Install Spark Cover Gasket 

The last step is to install the spark plug gasket in the rim of the spark plug well. They are circular in shape and are placed in a similar manner as that of a liquid sealant as the valve cover gasket. Screw all the nuts and bolts tightly. 

After this, all you have to do is place everything back in its position and make sure to rinse the oil off the parts by using the oil cleaner.

Contact Professionals 

Not everyone knows how to use mechanic tools and how to fix issues with their vehicle’s engine. If you are one of those, there is no need to panic. Instead of doing something wrong and creating more significant issues, getting your car checked by a professional is preferable. They have years of experience and know how to manage vehicle issues easily.

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