What to Spray in Spark Plug Hole?

What to Spray in Spark Plug Hole?

The spark plug bores located in the head of an engine’s block play a crucial role in its operation. These holes are responsible for supplying the necessary spark to light the fuel-air mix in the compression chamber, which ultimately creates the stroke that drives the engine. Needless to say, maintaining both holes for glow plugs and the spark plugs themselves is of utmost importance for achieving optimal engine performance.

To ensure the longevity and efficiency of these vital components, occasional maintenance or removal may be required. In such cases, it can be beneficial to utilize substances like rust inhibitors, liquid wrench, or even a small amount of gasoline. These aids can aid in the maintenance process, ensuring the cleanliness of the holes for glow plugs, functional, and free from any obstruction.

If you are looking for a thorough tutorial on just how to perform these procedures safely and effectively, then this post will give you the walkthrough directions and expert advice you need. By following these guidelines, you can preserve your plug holes and provide uninterrupted motor performance for years to come.

What to put in the gap of the spark plug?

What to put in the gap of the spark plug?

When dealing with a stuck or corroded glow plug, a rust penetrant spray or liquid wrench is an excellent choice. These substances are specifically formulated to seep into the rusted components and effectively loosen them, making the spark plug removal process much easier. It’s crucial to let the spray sit for a while, allowing enough time for it to thoroughly penetrate the rust and maximize its effectiveness.

Another option to consider is a dedicated spark plug cleaner solution, which offers additional benefits in removing carbon build-up and other forms of residue. This specialized product is intended to destroy stubborn deposits, ensuring optimal spark plug performance and longevity.

In some cases where the engine has been sitting unused for an extended period, a small amount of gasoline can be sprayed into the spark plug hole to assist in starting the engine. However, it is imperative to exercise extreme caution when using gasoline due to its highly flammable nature. Security should be a top concern at all times, and proper handling and storage of gasoline should be followed at all times.

By taking these extra steps and paying attention to detail, you can effectively address and overcome challenges associated with stuck or rusted spark plugs, ensuring smooth engine operation and prolonging the lifespan of your spark plugs. [1], [2]

What to put in the gap of the spark plug?


WD-40, renowned for its exceptional water-displacing properties, is an incredibly versatile tool that comes in handy when dealing with those stubborn spark plugs. When you spray WD-40 into the spark plug hole, its unique formula helps break down rust and grime, making the removal of the spark plug a breeze. Not only that, but WD-40 also acts as an outstanding moisture repellent, safeguarding your spark plugs against corrosion and extending their overall lifespan.

However, it’s important to note that while WD-40 works wonders for most cases, in severe instances of rust or build-up, it might not be the ideal substitute for a specialized spark plug cleaner or a dedicated rust penetrant spray. In such scenarios, it’s best to opt for more appropriate solutions. Nevertheless, when used as a preventative measure or for mild issues, WD-40 proves to be a reliable ally in your spark plug maintenance routine.

Remember, for optimal results, allow the WD-40 to sit for a while, enabling its penetrating properties to effectively dissolve rust and grime before you attempt to take out the plug.

Carburetor Cleaner

Carburetor cleaner is an incredibly effective solution which can be used for maintenance of glow plugs. Specifically formulated to dissolve tough grease, deep-seated dirt, and stubborn varnish, this powerful cleaner provides a comprehensive cleaning experience for your spark plug hole. Over time, residues can accumulate in the hole, hindering the spark plug’s performance.By carefully spraying the bore with the cleaner, you enable it to penetrate and break down these unwanted deposits, making spark plug removal a breeze and ultimately enhancing the overall performance of your engine.

To ensure maximum effectiveness, it is very important to let the cleaner stand for several minutes. This allows the cleaner to thoroughly break down any residue, making it easier to take out the plug. However, it’s important to be careful and observe appropriate precautions when handling carburetor cleaner. Due to its highly flammable and potentially harmful nature, it is recommended to use it in a well-ventilated area and avoid direct contact with skin or eyes.

By using a rich carburetor fluid during maintenance of your plugs, help ensure optimum efficiency and service life of the components of your engine.


Air Gun

An air gun, also known as a blow gun, is an invaluable tool for effectively maintaining the spark plug holes in your engine. This device utilizes the power of compressed air to forcefully and efficiently clear away any accumulated dust, grime, and other small debris that may have found its way into the spark plug hole.

Before using an air gun, it is crucial to ensure that the spark plug is securely fitted. This precautionary step helps to prevent any potential damage that could be caused by the high-pressure air.

To further enhance the cleaning process, you can spray a carburetor cleaner or WD-40 onto the spark plug. This will help break down any stubborn residue that may have formed. Once the cleaner has been applied, using an air gun can provide an additional level of cleaning, ensuring a thorough and complete removal of any remaining debris. This meticulous approach ensures a clean and clear pathway for the spark plug, optimizing its performance.

However, it is important to exercise caution when using an air gun. The force of the released air can cause particles to be propelled, which may pose a risk of harm. To protect yourself, always remember to wear safety goggles and gloves when operating the air gun.

By incorporating the use of an air gun into your maintenance routine, you can maintain the optimal condition of your spark plug holes, promoting the longevity and efficiency of your engine.

Air Gun


Oil, particularly penetrating oil, can be a highly effective and practical option for maintaining spark plug holes. Similar to a specialized rust penetrant spray, penetrating oil is specifically formulated to permeate stubborn rusted or stuck components, effortlessly easing their removal. This makes it an invaluable tool, especially when dealing with notoriously difficult and corroded spark plugs.

To utilize penetrating oil for this purpose, simply apply a small amount of oil into the spark plug hole, ensuring it reaches the rusted areas. Allow the oil to sit and thoroughly penetrate the stubborn rust, effectively loosening the grip of the spark plug. This process not only makes the plug easier to remove but also minimizes the risk of damaging the surrounding components.

Furthermore, the application of oil provides an additional layer of protection, helping to mitigate the chances of future rust and corrosion. By creating a barrier against moisture and environmental elements, oil acts as a safeguard, prolonging the longevity and optimal functioning of the spark plug hole.

However, it is crucial to exercise caution and ensure that all traces of oil are thoroughly cleaned out before starting the engine. Failure to do so may result in potential damage or adverse effects on the engine’s performance.

As always, it is essential to prioritize safety precautions when handling and utilizing oil in the engine. By following proper procedures, you can effectively maintain spark plug holes and contribute to the overall efficiency and reliability of your engine.

Brake Cleaner

Brake cleaner, a potent solvent, is specifically designed to effortlessly cut through stubborn grease and oil, making it an exceptionally effective product for cleaning spark plug holes. Its remarkable ability to evaporate swiftly without leaving any residue behind is crucial in maintaining optimal spark plug performance.

When using brake cleaner, it is recommended to carefully spray a small amount into the spark plug hole, ensuring thorough coverage of all inner surfaces. Allow the cleaner to sit for a few minutes, enabling it to effectively break down any lingering grease or oil present within the hole. Once the designated time has passed, the spark plug can be removed, revealing a noticeable reduction in grime and built-up residues.

It is important to note that brake cleaner possesses highly volatile and flammable properties, necessitating the observance of proper safety precautions during use. Always utilize this product in a well-ventilated area, ensuring it is kept away from any open flames or sparks. Additionally, for personal protection against accidental splashes, it is advisable to wear appropriate protective gloves and eye gear.

By following these detailed instructions and exercising caution, you can confidently utilize brake cleaner to achieve optimal cleaning results while ensuring your safety remains a top priority.

Brake Cleaner

How To Clean Spark Plug Hole?

Cleaning the spark plug hole is a critical and often overlooked aspect of engine maintenance that can significantly impact the performance of your vehicle. By taking the time to properly clean the spark plug hole, you can ensure that your engine runs smoothly and efficiently.

To begin the process, you will need a few tools and supplies. First, make sure you have a spark plug socket that fits your specific spark plug. This will allow you to safely remove the spark plug without causing any damage. Additionally, it is recommended to have a rust penetrant spray, such as WD-40, or a dedicated spark plug cleaner to effectively dissolve any rust or residue that may have accumulated in the hole.

To clean the spark plug hole, follow these step-by-step instructions:

  1. Start by carefully removing the spark plug from the hole using the spark plug socket. Take extra care not to damage the plug or surrounding components while doing this.
  2. Once the spark plug is removed, take a close look at it for any signs of rust or residue build-up. If you notice a significant amount of rust or residue, it is an indication that the spark plug hole itself requires cleaning.
  3. Now, it’s time to use the rust penetrant spray or spark plug cleaner. Spray the solution directly into the spark plug hole, ensuring that it reaches all areas. Allow the solution to sit for a few minutes to thoroughly dissolve the rust or residue.
  4. After the solution has had time to work, use an air gun to blow out the loosened rust and residue from the spark plug hole. It is vital to wear safety goggles and gloves during this step to protect yourself from any particles that may be blown out.
  5. Once the rust and residue have been cleared, take a clean cloth and wipe around the spark plug hole. Make sure to remove any remaining solution or debris, ensuring a clean and smooth surface.
  6. Finally, it’s time to reinsert the cleaned or new spark plug into the hole. Take care not to cross-thread it, as this can lead to further damage. Use the spark plug socket to tighten the spark plug securely.

By diligently following these steps, you can effectively clean your spark plug hole and maintain optimal engine performance. Remember, regular maintenance and attention to detail can go a long way in ensuring the longevity of your vehicle’s engine. [2], [3]

How To Clean Spark Plug Hole?


Can you put WD-40 in a spark plug hole?

Yes, you can use WD-40 in a spark plug hole. It’s beneficial for stuck or rusted spark plugs, acting as a rust penetrant and moisture repellent. WD-40 helps dissolve rust, ease spark plug removal, and protect against future corrosion. However, remember not to substitute it for a dedicated spark plug cleaner or rust penetrant. It’s best for prevention or mild cases of rust. Let WD-40 sit to effectively penetrate rust and grime before removing the spark plug. Follow safety precautions as it is flammable.

Is it OK to spray starter fluid in a spark plug hole?

Yes, it is generally safe to use starter fluid in a spark plug hole. Starter fluid, mainly composed of ether, helps start internal combustion engines. By spraying it into the spark plug hole, you provide extra fuel, aiding the engine starting in cold weather or when fuel is lacking. However, caution is necessary. Starter fluid should not be used as a regular solution for starting issues, as overuse can damage the engine due to its high combustion rate. Always follow the manufacturer’s instructions, reinsert and secure the spark plug tightly before starting the engine. Prioritize safety, avoid open flames or sparks, and wear protective gloves and eye gear.

Can I put gas in the spark plug hole?

Putting gasoline in a spark plug hole is technically possible, but highly discouraged due to safety concerns. Gasoline is volatile and flammable, posing a risk of fire or explosion near a spark plug. Excess gasoline can flood the engine, causing starting problems and diluting the oil, leading to insufficient lubrication and potential engine damage. It is recommended to use specialized engine starting products or penetrants instead. Always follow the manufacturer’s instructions and exercise caution when handling flammable substances.

Do you put anything on a spark plug?

It’s recommended to apply a small amount of anti-seize compound to the spark plug threads before installation. This prevents the plug from getting stuck in the cylinder head, especially in aluminum heads. Apply the compound sparingly, avoiding the electrodes to prevent misfires. Follow the manufacturer’s torque specifications to avoid over tightening and damaging the threads or breaking the plug. Apply a thin layer of dielectric grease inside the spark plug boot for a good electrical connection. Always wear protective gloves and follow safety guidelines for proper handling and installation.

Can you dip spark plug in petrol?

While it was sometimes used in older vehicles to assist with starting problematic engines, dipping a spark plug in petrol is generally not recommended due to the potential for harm. Modern fuel injection systems have made this practice unnecessary. Mishandling petrol can increase the risk of fire or explosion, especially when exposed to a spark or high heat. Excessive petrol on a spark plug can flood the engine, leading to additional starting issues and potential engine damage over time by diluting the cylinder wall oil. For a safer and more effective alternative, consider using a dedicated engine starting spray or penetrant if you encounter spark plug-related problems. Always prioritize safety and follow the manufacturer’s instructions when working with hazardous substances like petrol.

Does oil help spark plugs?

Oil is not typically used on spark plugs or recommended for spark plug holes. Its main function in an engine is to lubricate moving parts, cool the engine, and prevent corrosion. If oil gets into the spark plug well, it’s usually due to a problem like a leaky valve cover gasket or worn valve guides, and it can cause various engine issues. Oil-soaked spark plugs can lead to engine misfires, resulting in poor performance, reduced fuel efficiency, and potential long-term damage. If you notice oil on your spark plugs, it’s best to have a professional mechanic diagnose and fix the underlying problem. Always follow safety precautions and the manufacturer’s instructions when handling engine oil and spark plugs.

What happens if oil and gas mix in the spark plug?

When oil and gasoline mix in a spark plug, it can cause problems that affect engine performance. If these substances reach the spark plug, it can foul and fail to produce a spark, resulting in a misfire. This leads to a loss of power, poor fuel economy, and irregular engine operation.

In severe cases, excess gasoline and oil can cause carbon build-up on the spark plug, preventing it from functioning. This build-up increases the risk of a hot spot forming, leading to pre-ignition and engine knocking – a serious problem causing engine damage.

Furthermore, oil mixed with gasoline in the spark plug tube may indicate a more serious issue, such as a leaky valve cover gasket or worn valve seals. Promptly addressing these problems is crucial to prevent further engine damage. Always follow manufacturer’s instructions and safety precautions for engine maintenance.

Useful Video: What can you spray in spark plug hole?


Maintaining spark plugs is crucial for optimal engine performance. Using gasoline or oil on spark plugs can be hazardous and potentially damage your engine. It’s safer and more effective to use a dedicated engine starting product or penetrant for spark plug issues. Applying anti-seize compounds and dielectric grease can ensure spark plug longevity and overall engine health. Follow manufacturer’s instructions and safety guidelines for vehicle maintenance. Consult a professional mechanic for issues beyond your capabilities.


  1. https://www.repairsmith.com/blog/how-to-clean-spark-plugs/
  2. https://theautovibes.com/what-to-spray-in-spark-plug-hole/
  3. https://autoguidehub.com/what-to-spray-in-spark-plug-hole/