Six Reasons Oily Spark Plugs (on Threads and In Wells).

The engine's oil is essential for lubrication. Oil helps to prevent friction from excessive heat and excess heat.

It is important to avoid mixing oil, water and fuel. This can lead to engine failures, misfires, and more damage.

Oil can leak into the combustion chamber and get stuck to the spark plugs. But why is this happening? Let’s take a look at the most common causes of oil on spark plugs.

Índice de Contenido
  1. Why Oily Spark Plugs?
    1. 1. Leaking valve cover gasket
    2. 2. Clogged crankcase ventilation
    3. 3. A bad turbocharger
    4. 4. Check for worn intake valve seals
    5. 5. Broken piston rings
    6. 6. Pistons that are not working properly
  2. FAQs: Oil on Spark Plugs
    1. Do spark plugs need oiling?
    2. What if I have oil in my sparkplugs and want to drive?
    3. Is it possible for a misfire to cause oily spark plugs
    4. What is the best way to change oil in spark plugs?

Why Oily Spark Plugs?

A leaking valve cover gasket can lead to oily spark plugs. A clogged crankcase ventilation or a faulty turbocharger could cause oily spark plug electrodes.

This is a detailed listing of common oil causes for spark plugs.

1. Leaking valve cover gasket

Engine Oil On Spark Plug

You can be happy if your spark plugs are as shown in the photo above.

When the oil on your spark plug looks like this, and there is oil on the spark plug threads, it is not coming from the engine’s inside; it is actually coming from the outside from the valve cover, filling up the wells.

O-rings are found around the spark plug holes. They can either be integrated or external to the valve cover gasket. These O-rings can become brittle from heat and leak. Oil will then seep into the spark plug hole.

It can lead to misfires in the spark plugs or ignition coils.

You should replace your valve cover gasket as well as the O-rings surrounding the spark plugs if the entire spark plug has been covered with oil.

2. Clogged crankcase ventilation

Oil On Spark Plug Tip

You should be more worried if oil appears on the spark plugs' tips. An oily combustion chamber is never good news.

Most oil buildup on spark plugs can be caused by a blocked or defective crankcase ventilation. The crankcase can become clogged or faulty, causing an excessive pressure inside. Oil is forced into the combustion chamber by crankcase ventilation.

Check the crankcase ventilation breathing to ensure nothing is clogged, and the one-way breathing valves work fine – if equipped on your car model.

3. A bad turbocharger


Faulty turbochargers are also common in oiling spark plugs. Oil that leaks from turbo compressor seals can get trapped on spark plugs.

It can also happen due to poor crankcase ventilation. Make sure you check it out first.

You should check the oil level in your intercooler.

4. Check for worn intake valve seals

Valve Seal Around Valve Shaft

The Valves play a vital role in the combustion chamber by regulating the inflow of air and fuel while controlling exhaust gases’ outflow. The engine should never have fuel, oil or coolant mixed together. The oil could get into the crankcase combustion chamber if the valve seals fail.

Your car will start to emit blue smoke. It is important to have your valves checked immediately in order to avoid further engine troubles. This is how to identify bad valve seal symptoms.

5. Broken piston rings

Piston Ring Function

If you look closely at piston rings, compression rings can be seen at the top as well as the bottom. These rings will absorb oil as the piston moves upwards and downwards along the wall.

Oil from beneath the pistons is prevented by the rings. The rings eventually wear and oils find their way to spark plugs. It can prevent oil from getting to moving parts.

Learn more here about Bad Piston Rings symptoms.

6. Pistons that are not working properly

Car Pistons

A faulty piston can cause oil to leak into the spark plugs. Pistons are designed to operate at very high speeds and can be subject to wear.

The piston rings are most likely to be affected by oil. If there is damage or cracks in the piston rings, then the oil could find its way onto the spark plug.

To find out if your piston rings or piston rings have failed, you can either do a leak down-test or perform a compression test. It is highly advised to perform a leak-down test as this will help you identify these issues quickly.

FAQs: Oil on Spark Plugs

Do spark plugs need oiling?

The oil content of the spark plugs will determine if it is good or bad. If you find oil in the spark plug wells, it’s likely a bad valve cover gasket, which is fairly easy to fix. Internal oil combustion could also be a problem.

What if I have oil in my sparkplugs and want to drive?

No oil should be left on spark plugs. The ignition coil can be damaged if oil gets into the wells. Oil in the combustion chamber must be dealt with immediately to avoid further damage.

Is it possible for a misfire to cause oily spark plugs

A misfire won't cause oil to build up on spark plugs. A misfire could cause serious damage to your catalytic convert or other components, so make sure to get it fixed as soon as you can.

What is the best way to change oil in spark plugs?

You should replace either the valve cover gasket, or O-rings surrounding the wells if you see oily spark plug wells. It could also be caused by a bad turbocharger, or poor piston rings.

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