The Best Penetrating Oil for Stuck Spark Plugs (2023)

If you’re looking for a list of the best penetrating oils for stuck spark plugs, you’ve come to the right place, not only have our industry expert selected six of the best options on the market right now, but we’ve also clarified a few things you’ll need to know before going to buy one. As at the time of writing this blog post, we recommend Kroil Kano Penetrating Oil as the premium pick to go for; discover our picks below and keep reading our extensive thoughts on buying penetrating oils for your stuck spark plugs.

Under the hood of every vehicle, spark plugs dutifully perform their critical role- they ignite the fuel-air mixture that powers your drive. When they’re working smoothly, your engine hums with efficient performance.

But they’re not invincible, over time, due to corrosion, carbon build-up, or overheating, these engine heroes can turn into troublesome zeroes, stuck firmly in place, and hinder the engine performance. So, what’s the secret weapon to defeating this adversary? A penetrating oil.  

This miraculous substance has the power to worm its way into the tightest spaces, breaking down the barriers of rust and grime that imprison your spark plugs. But with so many options available, which one should you buy for battling against a stuck spark plug?

That’s where this technical guide will help you. We’ll break down the chemistry behind these wonder oils, compare the top-rated products in the market, and help you find the perfect oil for your needs.

Penetrating Oils Explained

Penetrating oil is a low-viscosity oil. It seeps into cracks, crevices, and threads of rusted and overly tightened nuts, bolts, and other fasteners like spark plugs, and helps to free them. Penetrating through the surface layer dissolves rust, reduces friction, and ultimately helps remove the stuck components.

Penetrating oils come in light, medium, and heavy-duty variants. Lighter oils are typically used for delicate components and preventive maintenance, while heavier-duty ones are applied to intensely stuck parts or those affected by extreme rust or corrosion.

In the case of stuck spark plugs, penetrating oil proves invaluable. It can prevent thread damage, ease removal, and even extend the spark plug’s lifespan.

Factors to Consider When Choosing a Penetrating Oil for Stuck Spark Plugs

If you’re considering buying a penetrating oil to remove stuck spark plugs, do consider these factors before making a purchase:

1. Viscosity and lubrication capability

The primary purpose of penetrating oil is to penetrate rust, corrosion, and debris around the spark plug threads and provide lubrication to ease the loosening process.  So, look for penetrating oils that have good penetrating properties and can effectively lubricate the threads.

2. Material compatibility

Some penetrating oils may contain harsh chemicals or have strong odors, which could pose safety concerns.

Before purchasing, ensure the oil is safe with the materials found in engine components, including metals, plastics, and rubbers.  Since spark plugs are the focus, you need products that do not corrode metal surfaces.

3. Ease of application

Penetrating oils are available in both spray and liquid forms. Spray formulations are convenient for reaching tight spaces and ensuring even application. The liquid formulation is usually available in the form of droppers. Some also come with specific spray nozzles to reach tough spots. Choose the one which is convenient for you.

4. Brand Reputation

Consider the reputation and reviews of the penetrating oil brand. Look for established brands like Kroil, FreeAll, and CRC, which are known for their quality products and positive customer feedback. Additionally, read online reviews and recommendations to get insights into the effectiveness of a particular penetrating oil.

Top 6 Penetrating Oils for Stuck Spark Plugs

The penetrating oil market is saturated with multiple products. So, it may be hard for you to decide which one suits your needs.

To make things easier, we have researched and listed one of the best penetrating oils that are suitable for removing spark plugs.

1. Kroil Penetrating Oil: The Premium Oil

A titan in the world of penetrating oils, Kroil has a reputation for top-tier performance. This premium quality penetrating oil seeps into minute spaces breaks down rust, and ensures easy removal of components.

Its secret formula removes carbon deposits without scratching your metallic part. Apart from spark plugs, it’s effective for breaking down rust and ensuring easy removal of bolts, fasteners, and other mechanical parts. However, it’s pricier than some alternatives.

2. CRC Screwloose Super Penetrant: The Quick Penetrating Oil

CRC is a renowned name in the chemical solutions industry for manufacturing oil and lubricants for various heavy industries. So is its product, CRC Screw loose Super Penetrant, which sets itself apart with its fast-acting formula.

You can easily spray it on your stuck spark plug. It will penetrate rapidly, giving you a short waiting period.

Its aerosol spray is available at a budget-friendly price, and you can even get more discounts if you choose to buy its 12-can pack.

The oil is also safe on most surfaces, reducing worries about potential damage. However, its smell can be off-putting to some users.

3. Free All Deep Penetrating Oil: A Budget-friendly Option

Free All Deep Penetrating Oil appeals to those who value cleanliness. A silicone-free formula leaves no residue behind, ensuring a clean working environment post-application.

It has been in the market for 40 years and performs admirably in loosening stuck parts. Despite its excellent performance, its 11 oz. The spray is available at a budget-friendly price of $11.93.

4. Liquid Wrench Penetrating Oil: Best Penetrating Oil Dropper

Liquid wrench oil offers a great balance between performance and value. While it may require a bit more patience, its effectiveness in loosening stuck parts is commendable.

The oil waste is reduced through the dropper, which can be applied only at the point of use. Thus, it’s an effective oil for removing spark plugs.

Liquid wrench claims that you can use it for seized painted metal joints, bolts, and even cleaning guns and sports equipment.

5. TrickShot Penetrating Oil: The Versatile Newcomer

Relatively new to the market, TrickShot Penetrating Oil shines with its versatility.

Whether dealing with stuck spark plugs or rusted bolts, it delivers impressive performance. It’s a 3-in-one spray that penetrates oil, lubricant, and degreaser.

6. WD-40: The Household Name

Its proven history makes it reliable in loosening stuck spark plugs. It’s easy to find and an affordable name in penetrants.

It comes with a straw nozzle to spray within seized components deeply. It’s an all-purpose loosening spray, which is safe on metal, rubber, or plastic parts.

Though WD-40 oil is widespread and has a versatile use case, it is less effective than specialized penetrating oils for more severe cases.

How to Use Penetrating Oil to Loosen Stuck Spark Plugs?

Loosening stuck spark plugs can be challenging, but penetrating oil can often help break free the rust and corrosion that may be causing the plugs to stick.

Here’s a step-by-step procedure on how to use penetrating oil to loosen stuck spark plugs:

1. Gather the necessary tools

You’ll need a penetrating oil (pick one of the products listed), a socket wrench with a spark plug socket, and a socket extension (if necessary),

2. Prepare the area

Make sure the engine is cool to avoid any risk of burns. Disconnect the negative terminal of the battery to prevent accidental electrical sparks. Also, remove any obstructions in the way of accessing the spark plugs.

3. Spray the penetrating oil

Locate the spark plug wires or ignition coils and follow them to the spark plugs.

Spray around the base of each spark plug where it meets the cylinder head. Make sure that the oil penetrates the area where the spark plug threads into the engine.

4. Let the oil penetrate

Allow the penetrating oil to sit and work its way into the threads for at least 15-30 minutes. This time will allow the oil to break down rust and corrosion, making it easier to loosen the plugs.

5. Attach the socket and wrench

Once the penetrating oil has had sufficient time to work, attach the spark plug socket to the socket wrench. Ensure that the socket size matches the spark plug size.

7. Loosen the stuck spark plug

Place the socket onto the spark plug and turn it counterclockwise (left) to loosen the plug. Initially, use steady and firm pressure, but be cautious not to apply excessive force to avoid damaging the plug or the engine.

If the plug doesn’t move, gently back-and-forth motions help break it free. You can use a breaker bar to provide additional leverage, but be careful not to overtighten it.

Wrapping it up

Choosing the right penetrating oil can significantly simplify removing stuck spark plugs. When selecting, consider the product’s viscosity, corrosion resistance, material compatibility, and ease of application.

Whether you opt for the trusted performance of Kroil or the versatile strength of FreeAll, you can free up your imprisoned spark plug. Once you use any of these products, share your experiences with us. We would love to hear your feedback.