What to Spray in Spark Plug Hole?

Dirt, debris, or oily substance are challenges a vehicle’s spark plug hole may contend with over time. These contaminants can hinder the proper functioning of the spark plugs.

Therefore, cleaning the spark plug hole is a crucial aspect of regular maintenance. However, knowing what to spray in spark plug hole is as important as performing the service in the first place.

So, carefully take your time to review the subsequent sections below to find out what is permissible in spark plug holes and how to clean the area.

what to spray in spark plug hole

What to Spray in Spark Plug Hole

Although there are several cleaning products in the automotive industry, not all are ideal for different vehicle parts. For example, the spark plug hole is a critical area in the engine. Therefore, the following are some of the cleaners like WD40, carb cleaner, brake cleaner, air etc., you can use in the hole.


Car owners often encounter the challenge of cleaning spark plug holes, a crucial aspect of vehicle maintenance. The debate over the best substance to use includes a variety of options. WD-40, known for its performance in displacing dirt, is a common choice. However, some drivers prefer using dedicated cleaning products as they are formulated specifically for such tasks. While WD-40 does a lot to clean, using the proper cleaner is key to resolving this issue without residue.

Carburetor cleaner

Cleaning spark plugs with carb cleaner is most likely the first recommendation from every auto technician. You can also spray carb cleaner in spark plug hole to get rid of hardened debris or dirt build-up.

Spraying Air by Air Gun

Cleaning a spark plug hole with carburetor cleaner alone may not completely eliminate the debris in the hole. So, you need another spark plug spray. An air gun is a complementary tool to help you blow out the residue of the debris in the hole. For new spark plug, only air is enough to clean.

Brake cleaner

Like carburetor cleaner, brake cleaner can also help as a spark plug hole cleaner. It can dissolve oil and gunk deposits in the spark plug hole. Meanwhile, you will also need a wire brush to clear off the debris in the spark plug.

How to Clean Spark Plug Hole (Steps)

Cleaning a vehicle’s spark plug hole can be pretty straightforward when you pay attention to details. The following is a step-by-step guide on how to clean wet black spark plug well.

Step 1: Disconnect the battery’s negative terminal

Disconnecting the battery is usually the first thing to do whenworking on virtually all components within the engine bay. It will help to prevent electrocution.

So, identify the battery, which looks like a big plastic rectangular box. Look for the terminal on top marked (–), loosen the cable, and take it off.

Step 2: Locate the spark plugs

Now, locate the spark plug wire. A couple of thick cables run from the carburetor to the engine’s top. Trace these wires to the top of the head cylinders. If your car uses ignition coils, you will see them on top of the engine.

Step 3: Blow out debris with an air gun

After that, get an air gun with compressed air and blow out debris or dirt from the ignition coil area to prevent the contaminants from entering the cylinder while removing the spark plugs.

Step 4: Disconnect the spark plug wires one by one

It is time to pull off the spark plug wires. Do this one by one to avoid confusing yourself with the wires and allowing dirt or debris into the cylinder. So, carefully hold the spark plug wire on the first plug by the boot and pull it off. Do the same for others.

Step 5: Remove the spark plugs

Get the spark plug socket and fix it on the end of an extension. Then, connect a rachet to the extension.

Now, place the socket on a spark plug and turn it counterclockwise to loosen it. After that, remove the socket and loosen the plug completely with your hand. Ensure to do this for all the plugs.

Step 6: Clean the spark plug hole

Once the plugs are out, get your air gun and fix a long tip (from the numerous tips) on the component. Then, place the tip into the spark plug hole and blow compressed air inside to eradicate debris, dirt, and other contaminants from the hole.

If you have oil in the hole, you can spray carb cleaner in spark plug holeto get rid of the oil. But, of course, you won’t leave the cleaner inside the hole. Therefore, the best approach is spraying it on a clean rag and using a big screwdriver and a cloth to clean the oil in the hole.

Step 7: Clean the spark plugs and set the gap

Now clean the spark plugs with the recommended spark plug cleaners, sandpaper, or wire brush. Then, set the gap according to the prescription in your car’s manufacturer’s manual.

Step 8: Install the spark plugs back in place

It’s time to install the spark plugs back in place. Carefully use a wrench with a rubber grommet to hold the spark plug and gently fix it.

Once you put the plugs into the hole, screw them by hand to avoid stripping the threads. Ensure to snug the plugs in with the socket and extension and tighten the plugs.

Step 9: Install the ignition coils and battery back again

Lastly, carefully install the ignition coils in place one by one and tighten the bolts. After that, start the car, allow it to idle for some time and see if it runs normally.


Can you put WD-40 in spark plug hole?

Spraying WD-40 in a spark plug hole is not a great idea. However, you can spray the solvent into spark plug tubes when you need to dissolve debris. After that, use a long screwdriver and cloth to clean the hole.

Meanwhile, carburetor cleaner is the best thing to use in your car’s spark plug hole. It can eradicate debris and other hardened dirt in the hole. Nevertheless, too much carb cleaner in a spark plug hole is also not good.

Can you spray starter fluid in spark plug hole?

No! Don’t spray starter fluid in an attempt to clean spark plug well. It can wash off the oil from the piston rings. When this happens, you may experience scratching or scoring of the cylinder walls.

Therefore, always stick to the recommended spark plug cleaner sprayfor your car. If you’re not sure of the exact product you need, you may want to contact your auto technician for advice.

Should I clean the spark plug hole?

Sure, you should clean your vehicle’s spark plug hole, especially if you see oil or dirt in the hole. You can use canned air or an air gun and a piece of cloth to clean it from the opening of the spark plug whole.

The air gun will help remove debris, dirt, or loose materials within the spark plug hole. However, carb cleaner is arguably the best spark plug cleaneryou can use alongside the air gun.

Can you put oil in spark plug hole?

Of course, you can put a little oil in a car’s spark plug hole to lubricate it properly. This is usually the case of a rebuilt engine or one that was abandoned without running for a long time. Also, putting the fluid will help lubricate the cylinder walls to enhance the first start-up.

However, you must avoid putting too much oil in the spark plug hole, as you may get a different reaction.

Will vinegar clean a spark plug?

Of course, vinegar is an excellent solvent to use when cleaning a spark plug. It can eliminate the carbon deposit on the spark plug, just like petrol. So, if you have a spark plug with lots of carbon deposit, kindly get a wire brush and vinegar or petrol.

cleaning spark plug hole

Firstly, use the wire brush to clear off some of the carbon from the spark plug. Then, take a moment to soak the spark plug in vinegar to clean the accumulated deposits.

Can I put gas or fuel in spark plug hole?

Yes, you can put a teaspoonful of gasoline in your car’s spark plug hole, especially when you need the component to fire up perfectly.

However, in this case, the intake manifold is the best place to put the fuel. Nevertheless, excessive gasoline in the spark plug area can cause severe engine challenges.


Knowing what to spray in spark plug hole is crucial when cleaning the component. Using the wrong cleaning product can cause severe damage to your car. So, ensure to follow the recommended products above.

 Also, carefully go through the step-by-step guide above to do the cleaning properly without skipping any vital steps.

Solomon Osuagwu

Osuagwu Solomon is a vetted auto mechanic with over ten years of experience in the garage and five years of experience as a service writer. He prides himself in writing accurate information on professional repair guides, DIY repair guides, buyer’s guides, comparisons, and car reviews. If he’s not in his repair garage, he’s writing automotive blogs to help car owners and fellow mechanics to troubleshoot and proffer solutions to several car problems.

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