Spark Plug Socket Sizes (In Metric and Standard)

When it comes to changing spark plugs, having the right tools can make all the difference.

In this article, we'll break down everything you need to know about spark plug sockets.

Discover the most common sizes and how to choose the right one for your vehicle, lawn mower, or other power equipment.

Print a copy of our socket conversion chart to help with metric vs SAE differences.

What is a Spark Plug Socket?

Spark Plug Socket Sizes

A spark plug socket is a specialized tool designed to remove and install spark plugs in an engine.

It features a rubber insert that grips the spark plug to prevent damage and ensure a secure fit during installation or removal.

The Most Common Spark Plug Sizes

The most common sizes of spark plug, and the ratchets required to remove and install them, are 5/8" and 13/16" for vehicles, and 3/4" for power equipment like lawn mowers.

They are available as part of some socket sets.

Socket Size (inches) Socket Size (mm) Common Application
5/8 16 Newer Small Engine Cars
13/16 20 Older Vehicle Engines
11/16 18 Motorcycle Engines
9/16 14 Newer Asian and Ford Engines
3/4 18 Motorcycles
3/4 19 Outdoor Power Equipment
7/8 22 Tractors

How to Measure Spark Plug Socket Size

To measure the spark plug socket size, you can use a caliper (measurement tool).

First, determine the diameter of the spark plug hex by placing the gap gauge or caliper over the hexagonal nut on the top of the spark plug.

Then, compare the measurement to the standard socket size chart to determine the correct socket size.

Compatibility with Different Spark Plug Brands

Spark plug sockets are compatible with different brands of spark plugs as long as the socket size matches the spark plug size.

Some popular spark plug brands include NGK, Bosch, Denso, and Champion, and each brand offers a range of spark plug sizes to fit various bolt patterns.

Always double-check the recommended spark plug size for your vehicle or power equipment to ensure compatibility with your spark plug socket.

Tips for Using a Spark Plug Socket

  • Use the correct size socket to prevent damage to the spark plug or the engine.
  • Ensure that the socket is clean and free of debris before use.
  • Use a ratchet or torque wrench to apply the proper amount of force when installing or removing spark plugs.
  • Make sure the engine is cool before attempting to remove or install spark plugs.
  • Always use a spark plug gap tool to check and adjust the gap before installation.
  • Apply thread lubricant to the spark plug threads, if needed, and ensure a secure fit.
  • When installing spark plugs, start by hand to avoid cross-threading and damage to the threads.
  • Tighten the spark plug to the recommended torque specification to avoid over-tightening or under-tightening.
  • Inspect the spark plugs and socket for signs of wear or damage before and after each use.
  • Store the spark plug socket in a clean, dry place to prevent rust or other damage.

Common Mistakes to Avoid

  • Using the wrong size socket, which can damage the spark plug or engine.
  • Forcing the spark plug, which can cause damage to the threads and make removal difficult.
  • Over-tightening or under-tightening the spark plug, which can affect engine performance and cause damage.
  • Failing to check and adjust the spark plug gap before installation, which can affect engine performance and cause damage.
  • Not using a thread lubricant, which can damage the spark plug threads and make removal difficult.
  • Cross-threading the spark plug, which can cause damage to the threads and make removal difficult.
  • Using a damaged or worn spark plug socket, which can damage the spark plug or engine.
  • Failing to properly secure the socket onto the ratchet or torque wrench, which can cause the socket to slip and damage the spark plug or engine.
  • Forgetting to disconnect the battery before working on the spark plugs, which can cause electrical shock or damage to the electrical system.
  • Using a spark plug socket for purposes other than its intended use, which can cause damage to the socket or tool.

When to Replace Your Spark Plug Socket

Replace your spark plug socket if it shows signs of wear or damage, such as cracks, chips, or rust.

A damaged socket can cause damage to the spark plug or engine, and may not fit properly, leading to difficulties with installation or removal.

I find that if the rubber insert is worn or damaged, it doesn't grip the spark plug securely, causing the spark plug to slip.

Socket Sets vs. Individual Sockets

When it comes to spark plug sockets, you have the option of purchasing a socket set or individual sockets.

A socket set typically includes a range of socket sizes, which can be useful if you work on different types of engines or vehicles.

If you only work on one specific type of engine, individual sockets are a more cost-effective option.

I recommend starting out with a set of spark plug sockets and buying individual spark plug sockets to replace worn or damaged sockets.

Deep vs Shallow Spark Plug Sockets

You have the option of choosing a deep socket or a standard socket.

A deep socket has a longer body than a standard socket, which can be useful if the spark plug is recessed or difficult to reach.

A deep socket can provide additional clearance to access the spark plug, making the installation or removal process easier.

I don't use a deep spark plug socket very often while fixing small engines because shallow sockets work well.

That being said, I prefer a deep spark plug socket while changing the plugs on my car because the plug holes are recessed.

Learn more about socket set sizes.