Blog Car Care Advice 8 Causes of Oil in Spark Plug Well (+ How to Remove It)
Car Care Advice

8 Causes of Oil in Spark Plug Well (+ How to Remove It)

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Have you noticed oil in your spark plug well? 
Are you seeing blue smoke from your exhaust

Here’s what happens with oil in the spark plug well:
When your spark plug’s well fills with oil, the seals or O-rings of the well deteriorate and start to leak.   

But there’s good news.
You can usually fix the leak by tightening the valve cover bolts. However, in some instances, you’ll need to replace the valve cover gasket and well seals.

Returning to the initial question, in this article we’ll discuss the eight most likely causes of oil in spark plug well. We’ll also cover how to remove the oil from your spark plug well, and answer four related FAQs

This Article Contains:

Let’s get started. 

The 8 Most Likely Causes of Oil in Spark Plug Well

Oil in your spark plug well can be caused by several factors. 
Let’s look at eight common causes of an oily spark plug:

1. Leaky O-rings

A leak from your O-rings or the spark plug tube seal is usually the main culprit behind the oil on spark plugs. 

The spark plug tube seals keep your spark plugs dry by keeping engine oil and coolant out. Failing O-rings can cause engine oil to leak into your spark plug well and onto your spark plugs.

2. Leaking Valve Cover Gasket

Your valve cover gasket sits atop your cylinder head and keeps oil away from the rest of your engine. A compromised valve cover gasket drains oil beneath an engine’s cover gasket resulting in oil seeping into the spark plugs well and eventually producing an oily spark plug.

Additionally, with a leaking cover gasket, your spark plug threads and matching ignition coil or spark plug wire could experience oil fouling.

3. Blown Head Gasket

Your head gasket prevents oil and coolant from mixing as they travel to the cylinder head. 

Coolant in the compression chamber is what most people associate with a blown head gasket, but an oil leak is also possible. When that happens, it’s common for oil to get into the combustion chamber and leak into your spark plug threads and wells.

You’ll notice excessive smoke and also some oil in your coolant reservoir. There might even be some oil on the tip of your spark plugs. 

When you spot these symptoms, you must replace the head gasket before the problem worsens.

4. Compromised Plug Well Grommets

Many engines have specialized grommets to prevent oil from seeping into the plug wells. However, these grommets suffer from age and heat distortion, so they provide reduced defense over time.  

5. Worn Valve Seals or Guides

Your intake and exhaust valves are centered by corresponding guides, each containing a special stem seal that prevents oil from entering the combustion chamber. With time, the stem seal can wear out and allow oil to flow where it usually doesn’t.

Blue smoke from your exhaust, finding oil, or ash in the spark plug wells are common symptoms of a failing valve guide. A malfunctioning valve guide can cause serious engine problems, so you should have your valve seals repaired immediately. 

6. Failing Piston Compression Rings

A combustion engine has pistons with compression rings at the top and bottom. These rings are set in the piston’s grooves and assist with clearing excess oil from the cylinder walls and preventing oil from getting into the combustion chamber.

If a piston ring fails, oil can enter the spark plugs wells. Another sign of bad piston rings includes increased blue exhaust smoke that smells oily.

7. A Cracked Piston

A cracked or compromised piston can also cause spark plug oil contamination. When this happens, it lets oil leak from the crankcase into the cylinder—where the damaged piston is.

This can cause excessive oil combustion and rattling noises.

8. Clogged Crankcase Ventilation

A clogged crankcase ventilation valve (PCV valve) allows oil to enter the combustion chamber from your oil pan — causing spark plug fouling. You can identify spark plug fouling by checking for oil deposits on your spark plug tips.

So we’ve figured out what could be causing the oil in your spark plugs well. 
Now let’s learn how to remove the oil! 

How to Remove Oil From Your Spark Plug Well

You can remove oil from a spark plug well in numerous ways. A shop towel is probably the most effective way to clean the spark plug hole. 

Try following these steps:

  1. Detach each spark plug wire or coil pack and use a spark plug socket wrench to remove the affected spark plugs. 
  1. Before attempting to soak up any contaminant, you should use a small amount of brake cleaner to thin out the oil.
  1. Tuck the towel into the spark plug well using an extension or another elongated tool.
  1. Leave the towel in place for 10-20 minutes, allowing enough time to soak up the excess oil.

Now that our wells are clean, let’s answer some burning questions regarding oil in spark plug wells. 

4 FAQs about Oil in Spark Plug Well

Here are the answers to four FAQs regarding oil on the spark plugs: 

1. What Symptoms Indicate Oil on My Spark Plugs?

If you’re experiencing any of these symptoms, your spark plugs might be experiencing oil contamination:

2. What’s the Cost of Cleaning Oil From Spark Plugs?

It’s always best to have a professional mechanic perform any repairs and maintenance on your vehicle. Since no parts are required for this service, it’ll cost around $106 – $130.

3. Can I Drive With Oil on My Spark Plugs?

Yes, technically, your vehicle can still drive with oil on your spark plugs. However, you’re going to want to figure out the source of the oil. 

Why’s that? 
Oil on your spark plugs can indicate more severe problems. The real issue isn’t the oil in your spark plug hole but how the oil got there, as the source is what can damage your engine.

4. Can Water in Spark Plug Wells Cause Misfires?

Interestingly, water in a spark plug well can also cause an engine misfire

Water can cause your electrical system to short-circuit and prevent the spark plug from firing properly. That’s not all, it can also result in rough idling, reduced power, and increased emissions.

Additionally, leaving water behind can cause the ignition system or other electrical components to rust. That’s why you must deal with any water in the spark plug well as soon as possible. This’ll prevent damage to the engine and ensure proper engine performance.

Final Thoughts

Having oil in your spark plug well is a simple fix, but it’s always best to leave any maintenance or repairs to the professionals. 

AutoNation Mobile Service offers a mobile mechanic service with qualified technicians available seven days a week.

From ignition coil replacements and a simple oil change after experiencing an oil leakage to a piston ring replacement, AutoNation Mobile Service technicians will come straight to your driveway to deal with them. 

We also provide a 12-month | 12,000-mile warranty and upfront pricing on all repairs.

Book a spark plug check-up via our easy and convenient online booking system