Informational Guide

What To Do When Oil Is On a Spark Plug

Is there supposed to be oil on spark plugs? No, if you find oil on the spark plug, there is a problem. We look at the top causes, issues, and how to fix them.

The spark plug is an integral part of the car's ignition system. Are spark plugs supposed to have oil on them? No, if you find oil on the spark plug, there is a problem that must be addressed.

In this guide, we cover what to do when the spark plug has oil on it and some of the top oil on spark plugs symptoms.

The most obvious sign that something is wrong is when the spark plugs have oil on them. However, you might notice other symptoms that cause you to look at the spark plugs in the first place.

  • Decrease in engine performance 
    If the spark plug is allowed to contact the motor oil, it can't create the proper spark for ignition. Because of this, you might see a decrease in acceleration as the spark plug malfunctions.
  • Possible engine misfires 
    Will oil on the spark plugs cause misfires? An incomplete combustion of the fuel-air mixture leads to misfires. If there is oil on one spark plug, it's possible to notice some hesitation, shaking, or misfiring.
  • Blue smoke from the tailpipe 
    If you notice oil on spark plugs with Ford Focus models, it can dramatically affect how the engine burns its fuel. When unburnt fuel makes it through the system, the exhaust might pour out blue or white smoke.
  • Gas smell from exhaust pipe 
    If there is oil on one spark plug and the fuel doesn't get burnt, you may smell the gas through the exhaust. These fumes might be most noticeable when the engine is cold or right after it has been started.
  • High fuel consumption 
    Any time the engine doesn't run efficiently, you risk spending more on fuel. The engine is going to work more than it needs to, which means that you will be at the pump more often than normal.
Oil On Spark Plug

Spark Plugs Have Oil On Them? 5 Most Common Causes Discussed

If you continue to drive with oil on the bottom of a spark plug, you could cause further damage to your vehicle. In fact, you might damage the catalytic converter, which is a very expensive replacement. Why is there oil on my spark plugs?

When there is engine oil on the spark plug threads, it could be due to one of these causes.

Leaking Valve Cover Gasket

The valve cover gasket is responsible for keeping motor oil on the cylinder heads while keeping it away from parts that don't need oil. Over time, high temperatures and age will cause the gasket to leak. 

What does oil on a spark plug mean? In this case, it could mean that you need a new valve cover gasket. It's possible that your oil on spark plug in a snowmobile may also be caused by this problem.

Old Valve Guide Seals

The valve guides also wear out over time from the constant movement of the valves that pump oil into the combustion chamber. When the valve guide seals wear out, you might notice oil on the spark plug threads.

Left untreated, this condition will cause more problems that can cost more to repair. Various seals can also be the cause for oil on a spark plug in lawnmowers.

Bad O-rings

The overhead camshaft engine, whether it is single or double (SOHC/DOHC), has a spark plug O-ring. Over time, the constant heat can degrade this seal and allow oil into the spark plugs. This problem occurs when the spark plugs have oil on the threads.

Broken Piston

What causes oil on spark plugs? If you notice oil on the spark plug tip, it's possible that you have a broken piston. While this condition is less likely than the others, a broken piston could allow pressure from the oil pan to pass into the combustion chamber, where it can pump oil onto the tip or threads.

Failing Piston Rings

Why do my spark plugs have oil on them? More commonly, it's caused by a broken compression ring. Again, this will cause the pressure from the oil pan to pass into the combustion chamber, where it can pump oil onto the tip or threads. This could also be the reason there is oil on a spark plug in motorcycles.

What Causes Oil On Spark Plugs

How To Find Out What’s Causing Oil On A Car’s Spark Plugs

Before you can learn how to fix oil on spark plugs, you need to figure out what is causing it first. In some cases, you might be able to troubleshoot it yourself, while other times, it's best to trust a professional.

Perform visual inspection

If you have an OHV engine, you can perform a visual inspection of all the outside areas of the cylinder heads. If you notice oil coming out of the valve cover gaskets, you need to replace them. 

With SOC/DOHC engines, you can also perform a visual inspection, but you should also look at the condition of the spark plugs themselves for signs of oil. If there is oil on the wires or plug coating, it's time to replace the O-ring seals.

Run an engine test

Most of the time, the visual inspection will be enough to figure out the problem. In some other cases, you will need an engine test for additional diagnosis. These are usually done by a mechanic and could be performed as an engine compression test or engine differential pressure test.

If you have the right tools and some mechanical expertise, you may be able to perform these tests at home.

How To Fix Oil On Spark Plugs: Top Tips From A Mechanic

Do you want to know how to stop oil from getting on the spark plugs? We will examine some solutions, but you should never work with your spark plugs unless you have experience. You could damage your engine very easily if you don't know what you are doing.

  1. 1
    Figure out the cause of the problem.
  2. 2
    Remove the valve covers by taking out the bolts. If it is adhered to the head tightly, you might need a rubber mallet. Don't ever use a metal tool to pull it out.
  3. 3
    Take out each spark plug with your removal socket. Before you change the spark plugs, inspect each one for oil. Can you clean oil off spark plugs? Yes, you can clean spark plugs. Just use a wire brush to clean them off.
  4. 4
    Take off the old gasket and O-ring seals.
  5. 5
    Clean the cylinder head and valve cover surface to remove the old gasket. Don't use any metal tools.
  6. 6
    Install the new O-ring seals and gasket. Make sure you choose the appropriate part for your vehicle. Put new spark plugs in. Make sure you have the right spark plug gap
  7. 7
    Once everything is put back together, you should take your vehicle for a test drive. Also, it helps to monitor the health of the spark plugs over time to ensure you have fixed the problem.

Preventing Oil On Spark Plugs In The First Place

If you don't want to deal with oil on the spark plug threads, you can take several steps to prevent it from occurring.

First, you should maintain your vehicle as per the instructions in your service manual. Additionally, it helps if you repair any problem the second you notice it is occurring. By leaving things unrepaired that are malfunctioning, you only allow bigger problems to happen down the road.

People Also Ask (FAQs)

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

The spark plugs are responsible for the ignition of your vehicle. When oil saturates the plug, it can stop the ignition system from working correctly, which could keep your car from starting.

Can oil ruin spark plugs?

Yes, there should never be oil on spark plugs in a Honda Civic or any other vehicle. The oil will cause the spark plug to foul, requiring a replacement.

How long does it take to see the symptoms that there is oil on the spark plugs?

Depending on how much oil has made its way to the spark plugs, you could see symptoms right away, while other times, it could take a while. At the first sign of trouble, have the spark plugs looked at.

Can you still drive with bad spark plugs?

You can drive with bad spark plugs, but it will lead to poor engine performance, a decrease in fuel economy, and it could cause your vehicle to break down.


If you notice oil on a spark plug, it's time to take action. Your simple steps today can help you improve engine performance and ensure that other vital parts continue to run as they should.