What size socket for motorcraft spark plugs?

Most Motorcraft spark plugs use a 5/8-inch hex, so the standard socket is a 5/8-inch spark plug socket. Some engines with larger plug heads may require a 13/16-inch socket. Always verify the exact hex size for your plug model in the service manual or by inspecting the plug.

In this article, we break down the common socket sizes you’ll encounter with Motorcraft plugs, how to identify the correct size for your engine, and best practices for safe removal and installation. The goal is to help you avoid damage to the plug or cylinder head and complete a reliable installation.

Common socket sizes you may encounter

Before listing the sizes, note that the vast majority of Motorcraft plugs fitted to Ford-family engines use a 5/8-inch hex, with a smaller subset requiring a larger 13/16-inch hex. The following sizes cover the most frequent scenarios you’ll see in the field.

• 5/8 inch (16 mm) hex: The standard size for the majority of modern Motorcraft plugs. Use a 5/8" spark plug socket, typically with a 3/8" or 1/2" drive.


• 13/16 inch (21 mm) hex: A larger hex found on some engines or specific high-performance applications. If the plug looks larger or won’t fit a 5/8" socket, measure the flats or consult the manual to confirm.

Conclusion: If you’re unsure which size your engine needs, check the owner's manual, service data for your vehicle, or measure the plug hex directly to avoid using the wrong socket.

How to verify the correct socket size for your Motorcraft plug

Before you buy or attempt removal, use these steps to confirm you have the right tool:

1. Identify the exact Motorcraft plug model installed (or the engine code/year) and look up its hex size in official specs or the service manual.


2. Inspect the plug head for a stamped hex size; if there’s no stamp, measure across the flats with a caliper or ruler.


3. Compare your measurement: about 0.625 inches indicates a 5/8" socket; about 0.8125 inches indicates a 13/16" socket.


4. Choose a spark plug socket with a rubber insert to securely grip the hex and a depth that reaches the plug head without bottoming out.


5. If in doubt, bring the plug or engine details to a parts store or service shop to confirm the correct size before attempting removal.

Conclusion: Correctly identifying the hex size helps prevent stripping the plug or damaging the cylinder head, and ensures a smooth installation.

Tips for safe removal and installation

With the correct size identified, follow these best practices to protect the engine and achieve a proper seal:

• Use a deep, magnetized or rubber-insulated spark plug socket designed for spark plugs to avoid dropping or cross-threading.


• Follow manufacturer guidance on anti-seize; many modern engines do not require it, while some older specs do.


• Apply the correct torque specified by Ford/Motorcraft for the vehicle when reinstalling; overtightening can damage the threads.


• Take care to thread plugs in straight and by hand at first to prevent cross-threading, then finalize with a torque wrench if required.

Conclusion: Proper tool choice and technique reduce the risk of damage and help ensure reliable ignition performance.

Summary

For most Motorcraft spark plugs, expect a 5/8-inch hex socket; some models may require a 13/16-inch. Always verify the exact size for your plug by checking the model/spec sheets, measuring the hex, or consulting the service manual. With the right socket and careful technique, you can replace Motorcraft plugs safely and effectively.

What size socket for Ford spark plugs?

The most common Ford spark plug socket sizes are 5/8 inch (16mm) for many models and 9/16 inch (14mm) for specific applications like some EcoBoost and Triton engines. Some older or larger engines may use a 13/16 inch socket, and some newer European and Asian-built Fords use 14mm (which is the same as 9/16 inch). Always verify the correct size for your specific year, make, and model to ensure a proper fit and avoid damage.
 
This video demonstrates how to replace spark plugs on a Ford F-150: 1m1A Auto: Repair Tips & Secrets Only Mechanics KnowYouTube · Sep 26, 2023
Common spark plug socket sizes for Ford vehicles

• 5/8 inch (16mm): This is a very common size used in many Ford models. It's often referred to as the standard spark plug socket size. 
• 9/16 inch (14mm): This size is frequently used in specific Ford applications, particularly on some EcoBoost engines and certain Triton engines. 
• 13/16 inch (20mm): This is used on older or larger engine Ford vehicles. 
• 14mm: This is the metric equivalent to 9/16 inch and is found on some newer European and Asian Fords, as well as EcoBoost engines. 

You can watch this video to see how to remove spark plugs on a Ford EcoBoost engine: 40sSuburban RanchYouTube · Aug 15, 2025
Tips for choosing the right socket

• Check your owner's manual: This is the most reliable way to determine the correct socket size for your vehicle. 
• Consider a spark plug socket set: If you work on multiple vehicles, a set that includes common sizes and is designed with a rubber insert or magnet to hold the plug can be a worthwhile investment. 
• Use a "spark plug socket": These are specifically designed with a rubber insert or magnet to grip the spark plug, hold it securely, and help remove it from deep-set wells. They also protect the spark plug from breaking. 

What size socket is a Ford F-150 spark plug?

9/16 inch
Product Summary: OTC 6900 Ford F-150 Spark Plug Socket, Gray
This unique and patented design works on 2004–newer Ford F-150 pickup trucks with 5.4L 3-valve Triton V-8 engines. The socket end is 9/16 inch and the soft rubber insert holds and protects spark plug during removal and installation.

What cars use 14mm spark plugs?

• This 12 point 14mm spark plug socket is compatible with 2007+ BMW 3.0L turbocharged engines such as the N54, N55, N20, N26, S55, N63, B46, B48, and B58.
• Along with certain BMW engines, our thin wall spark plug socket is compatible with a variety of MINI vehicles such as the R55, R56, R57, and R60.

What size socket do I need for a RC12YC spark plug?

The correct spark plug socket size for a Champion RC12YC is a 5/8-inch socket. Some sources also list the equivalent metric size as 16mm. 
You can watch this video to see how to replace the spark plug on a lawnmower: 59sNKY DIYYouTube · May 3, 2021

• Socket size: 5/8 inch
• Metric equivalent: 16mm
• Application: This size is common for many small engines, including those on lawnmowers, snowblowers, and some cars.