Why There Is Oil On Spark Plugs Threads? [Easy Fixes]

If you are performing some routine maintenance on your car and you pull out your spark plugs only to find that there is oil on them. You might get somewhat concerned. Because spark plugs aren’t supposed to have oil on them. If you find oil on spark plugs threads then there’s something wrong with some other component of your engine.

In this article, we’ll be going over the various issues that can leave your spark plugs in this state. Let’s get started.

Reason Behind The Oil On Spark Plugs Threads?

The presence of oil on your spark plugs can be caused by several possible issues. Let’s see what they are:

1. Leaky O-Rings:-

These O-rings keep oil and everything else on one side of the spark plug, and the other side remains dry. The O-rings for your spark plugs are located within the valve cover. If you only have oil on one spark plug, you might have a leaky O-ring seal. This is one of the best outcomes if you have oil on your spark plugs. However, you still need to address the problem as soon as possible. Leaky O-ring seals can cause your engine to misfire and lead to more extensive damage.

2. Broken Valve Cover Gasket:-

The most important gasket among tons of different gaskets in the engine is the valve cover gasket. This gasket sits in between the valve cover and the top of the cylinder head. It is used to create a seal between these two components of the engine. The valve cover gasket is there to keep all of this oil where it belongs.

Exactly like the O-rings, the valve cover gasket in your engine is likely made out of rubber or silicone, which makes it more likely to fail due to the high temperatures. If your valve cover gasket is leaking, you’ll likely see oil on spark plugs threads.

3. Broken Head Gasket:-

The head gasket is located between the bottom of the cylinder head and the engine block. It is the most important gasket in the whole car. Its purpose is to maintain a seal between these two parts. Which allows oil and coolant to circulate through the engine without leaking out. It also keeps the combustion chamber airtight. Both of these things are incredibly necessary for your engine to work properly. While coolant in your compression chamber is what most people associate with a blown head gasket, another fluid that could be leaking is oil. When that happens, it’s common for oil to get into the combustion chamber.

4. Broken Piston:-

The Pistons allow your engine to turn combustion into rotational force. The pistons are right up in the combustion chamber because of that they inevitably end up being exposed to a lot of heat. If a piston gets overheated, it may end up cracking. Whenever a piston is cracked, it can allow oil to make its way up past the piston and into the combustion chamber. Where it will eventually cover the spark plugs.

5. Faulty Piston Compression Rings:-

Around each piston in your engine, there are compression rings that keep oil from seeping into the combustion chamber. When these compression rings are damaged. You will see oil on spark plugs threads. These rings keep everything running smoothly and prevent more significant problems. Therefore, if you suspect damaged compression rings, it’s best to repair them as soon as possible.

6. Worn-Out Valve Guides:-

The valve guides within your engine have two functions. One of these is to protect the valve stems from being worn out, and the other function is to ensure that the valves are properly lined up with their valve seats. If the valve guides wear out, the valves won’t be able to create a proper seal within the combustion chamber, which can cause a vacuum that can draw oil into the spark plug wells.

Hence, these are some basic reasons for this cause.

How To Fix The Issue Of Oil On The Spark Plugs?

If there’s an oil on spark plugs you might be wondering what you need to do to get it out. Let’s see how to deal with it.

Step 1:-

First and foremost, you need first to turn off your car and then proceed to disconnect your car battery terminals. This will ensure that the engine is off and not supplying power.

Step 2:-

To inspect the head gasket, you must remove the valve cover with a screwdriver. The seals and gaskets will also be exposed. If an inspection points to the head gasket as the culprit for oil on spark plug threads, you’ll need to replace it right away.

Step 3:-

Spark plugs are built into the valve cover. Therefore, to replace them, you must remove the valve cover first. Before this step, take out the spark plug tubes and put them on the side. Here are the few steps through which you can remove spark plugs properly.

1. Once it is done, next take the clamps off the hoses that go to the valve cover using pliers that can easily unlock them. Afterward, you can use your hands to remove the hose.

2. Then, remove the wiring harness from the top of the valve cover. Once accomplished, now get a big socket and power handle to take the nuts out of the valve cover. For this, make sure to remove the nuts one by one with the tools unless it is easy to pry them loose with your hands.

3. Now, get the screwdriver and pry under the valve cover as it is often stuck on. With the little wiggling and prying, one can easily get it off.

4. Now after the valve cover is removed, the seals located in each of the spark plugs can be removed.

Step 4:-

You need to clean the head and valve cover before installing new gaskets and seals. Cleaning these parts helps remove old particles and thus helps the new parts you are installing to have a tighter seal.

Step 5:-

You need to get the gasket as per the shape of the component is essential. Check the material and the quality of the gasket, before purchasing it for the vehicle. Normally, the high-quality silicone material is considered good for the durability of the car and the valve cover gasket.

Step 6:-

Once you are done with it, add a liquid called sealer at the edges so that the new gasket doesn’t slip over. The gasket placed over the liquid sealer will tightly secure its place.

Step 7:-

Lastly, there is a need to place the spark plug gasket on the rim of the spark plug well. These are actually circular in shape and are placed in the same manner using the liquid sealant as the valve cover gasket.

Step 8:-

Once finished with it, now bolt the nuts in the order 2-3-1-4 that were removed earlier, in order to avoid any damage to the valve cover.

Step 9:-

You need to place everything back in position and make sure to rinse the oil off the parts which would have spilled around) by using the oil cleaner.

Therefore, the spark plug’s role is quite larger than its size in the functioning of the engine. Therefore, it’s the responsibility of the car owner to keep a check on the condition of the engine and determine the problem.

Can You Drive With Oil On The Spark Plugs?

Yes, you can drive with oil on the spark plugs but there is a need to diagnose the reason behind how the oil got there as it can damage your engine.


We hope the above mentioned information about why there is oil on spark plugs threads will be helpful to all the readers. If anybody’s doubts persist feel free to comment in the comment section below. We’ll definitely try to solve your doubts as soon as possible.

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