What kind of spark plug socket do I need?

The basic answer is simple: you need a spark plug socket that matches the spark plug’s hex size, fits your ratchet drive, and includes a retention feature to hold the plug while you work.

Beyond that core requirement, you’ll want to consider socket length (standard versus deep), whether you prefer a magnetic or rubber insert, and the overall build quality to endure heat and torque in an automotive environment. The exact socket you choose depends on your engine’s specs, so verify the plug size before you shop.

Identify the plug hex size and drive compatibility

To start, confirm the spark plug’s across-flats hex size and pair it with the right drive size for your ratchet or impact tool. The socket must match that hex size exactly and fit your tool’s drive (3/8-inch, 1/2-inch, or 1/4-inch).

What to look for when selecting a socket:

• Hex size compatibility: the two most common are 5/8" (16 mm) and 13/16" (20.6 mm). Some specialty or older engines use other sizes, so check the plug specification or measure across the flats.


• Drive size: most passenger cars use a 3/8" drive; for tight spaces or low clearance, a 1/4" drive can help; for higher torque applications, a 1/2" drive is common.


• Length: standard depth works on exposed plugs; deep sockets reach recessed plugs; consider a stubby or compact socket for cramped engine bays.


• Retention: magnetic or rubber inserts help hold the plug during removal and installation, reducing the chance of dropping it into the engine bay.


• Construction: look for impact-rated sockets if you’ll use a impact wrench or expect high torque; chrome or polished finishes are common for hand tools.


• Contact type: 6-point sockets are generally preferred for spark plugs because they grip the hex better and reduce rounding; 12-point sockets are less common for this task.

Getting these details right minimizes the risk of damaging the plug or the cylinder head and makes the removal and installation smoother.

How to measure and confirm the right socket

When you’re unsure of the exact size, use a few quick checks to verify before buying or swapping sockets.

• Check the vehicle’s service manual or the spark plug manufacturer’s specs for the exact hex size.


• Measure the across-flats distance on the plug with calipers if you have an unboxed plug in hand.


• Match the measured hex size to a spark plug socket that has the same across-flats dimension.


• Consider space in the engine bay to decide between standard, deep, or stubby socket, and whether you need a wobble extension or universal joint.


• Opt for a retention feature (magnet or rubber) to keep the plug secure during removal.

In practice, trust the plug’s specification as the primary guide, then pick a socket that fits your drive size and offers adequate reach for your engine layout.

Common configurations you’ll encounter

Most everyday vehicles can be serviced with a straightforward setup, but there are variations you should know about.

• For the majority of modern passenger cars: a 3/8" drive spark plug socket, deep or standard length as needed, with a 6-point hex and either a magnetic or rubber retention insert; hex size is typically 13/16" or 5/8" depending on the plug.


• For tight engine bays or recessed plugs: a short or stubby socket with a 3/8" drive plus a wobble extension to improve alignment without stressing the plug.


• For heavy-duty or high-torque scenarios: an impact-rated socket with a robust magnetic insert to keep the plug in place during removal and installation.

These configurations cover most common scenarios, but always confirm the exact plug size for your specific vehicle or equipment before purchasing a socket set.

Special cases and practical tips

Accessing recessed plugs

When plugs sit deep in the cylinder head, choose a deep socket with a short or specialty extension and, if needed, a wobble joint to align the socket without bending or stressing the plug.

Extensions, wobble joints, and alignment

A wobble extension or universal joint helps the socket reach at odd angles, reducing the risk of cross-threading or dropping the plug in tight spaces.

Summary

To choose the right spark plug socket, identify the plug’s hex size, select the appropriate drive size for your tool, and decide on depth and retention features that fit your engine’s layout. A 5/8" or 13/16" hex size with a 3/8" drive is common for many cars, but always verify the exact specification for your engine. Prioritize a socket that offers a secure hold on the plug (magnet or rubber insert), adequate reach, and robust construction to ensure a smooth, safe maintenance experience.

Additional notes

Having a dedicated spark plug socket on hand can prevent damage to the plug and cylinder head, reduce the risk of dropping a plug into the engine, and make future maintenance faster and more predictable.

Are spark plug sockets special?

Yes, spark plug sockets are different because they have unique features like a rubber insert to protect the plug's porcelain and grip it for removal and installation, and they are often deeper than standard sockets. They also come in a wide variety of sizes, including common ones like 5/8" (16mm) and 13/16" (20mm), to fit different engines and their specific spark plug designs.
 
You can watch this video to learn about the differences between a spark plug socket and a regular socket: 1mAuto CareYouTube · Apr 12, 2025
Key differences

• Rubber insert: Spark plug sockets contain a rubber insert that protects the spark plug's porcelain insulator from cracking and helps hold the plug securely during installation and removal. A standard socket lacks this and could break the plug. 
• Depth: They are typically deep-well sockets to reach the spark plugs located down in narrow and deep cylinders. 
• Grip: The rubber insert provides a better grip, making it easier to lift the plug out of the engine once it's loosened. 
• Wall thickness: They are often designed with a thinner wall than standard sockets, which is crucial for fitting into the confined space where spark plugs are located. 
• Design: Some are designed as "glow plug sockets," which have a universal joint for flexibility to access hard-to-reach cylinders. 

This video explains the purpose of the rubber insert in a spark plug socket: 1mDanny Johnson’s GarageYouTube · Aug 6, 2025
Common sizes

• 5/8" (16mm): Most common size for newer vehicles, motorcycles, and small engines. 
• 13/16" (20mm): Frequently used on older and large-engine vehicles. 
• 9/16" (14mm): Commonly found in Ford vehicles and some newer European and Asian cars. 
• 3/4" (18mm or 19mm): Used for various small engines, motorcycles, and some older GM vehicles. 
• 7/8" (22mm): Used in aviation, tractors, and some older vehicles. 

You can also watch this video to learn about the different sizes of spark plug sockets: 53sCatus MaximusYouTube · May 16, 2020

How to know which spark plug socket to use?

For the majority of plugs, you need a 5/8” or 16mm socket. Some Fords use 9/16″ plugs, some newer European and Asian vehicles use 14mm plugs, and there are a few applications that use 7/8″, 13/16″, ¾” or 18mm plugs. All spark plugs are 6 sided, except some BMW engines.

Are spark plug sockets universal?

No, spark plug sockets are not universal and come in several sizes, including common ones like 5/8"5 / 8 "5/8" and 13/16"13 / 16 "13/16", as well as metric sizes like $14$mm and $18$mm. The specific size needed depends on the vehicle's engine, and using the wrong socket can damage the spark plug. 
Common spark plug socket sizes

• 5/8"5 / 8 "5/8" (often used for smaller engines)
• 13/16"13 / 16 "13/16"
• 3/4"3 / 4 "3/4"
• $14$mm
• $18$mm
• 9/16"9 / 16 "9/16" (often used for some Ford vehicles) 

Why a universal socket doesn't exist

• Different engine types: Engines, from cars to chainsaws, use different spark plugs that are manufactured in different sizes, necessitating different socket sizes, say Quora users. 
• Metric vs. imperial: Some vehicles use metric-sized plugs ($14$mm, $18$mm), while others use imperial (5/8"5 / 8 "5/8", 13/16"13 / 16 "13/16", etc.). 
• Risk of damage: Using the wrong size socket can damage the spark plug's hex, making it difficult to remove, or strip the threads in the cylinder head, according to a YouTube video. 

How to find the right socket

• Check your vehicle's owner's manual for the specific spark plug and socket size required, recommends CarParts.com. 
• Purchase a set of spark plug sockets to ensure you have the correct size for your vehicle. 
• Consider a specialized socket with a rubber insert or magnet to hold the spark plug, which makes installation and removal easier. 

Do you need a special socket to take out spark plugs?

Yes, you generally need a spark plug socket to remove a spark plug, as standard sockets won't be able to grip and hold the plug once it's loosened. Spark plug sockets have a rubber insert, magnet, or clip to securely hold the plug, which is especially important for spark plugs in hard-to-reach, deep-set engine wells. 
Why a spark plug socket is needed

• Grip: The main function of a spark plug socket is to grip the plug once it's removed from the engine. Standard sockets have nothing to grab onto the tip and will simply drop the plug. 
• Protection: The rubber insert or magnet also protects the spark plug's ceramic insulator from damage during removal and installation. 
• Deep wells: For engines where the spark plugs are recessed, the socket with an extension is essential for reaching and extracting the plug. 

This video explains why you need a spark plug socket to remove a spark plug: 54sRams to the RescueYouTube · Mar 7, 2025
What to do if you don't have one

• Use a substitute: While a dedicated socket is recommended, you can sometimes use a regular deep socket of the correct size, but you'll need a method to grab the plug afterward. Some mechanics have used techniques like putting a piece of butyl tape or masking tape inside a regular socket, or using other tools like long needle-nose pliers or even a piece of flexible hose that fits over the plug's tip, as shown in this YouTube video and described on Quora. 

You can watch this video to learn how to remove a spark plug without a spark plug socket: 1mJoe's DIY LabYouTube · Jul 11, 2024
Other tips for removal

• Use the right size: Most spark plugs require a 5/8” or 16mm socket. 
• Use an extension: You will almost certainly need an extension to get the socket down to the plug, which you can attach to a ratchet. 
• Turn counterclockwise: Gently turn the ratchet counterclockwise to loosen the plug. If it feels stuck, don't force it.