What size are the spark plugs in a Mustang?

The spark plugs in most modern Ford Mustangs use a 14 mm thread diameter, but the exact reach (how far the plug seats in the cylinder head) and heat range depend on the specific engine and year. In practice, you should verify the size for your exact model, but this article breaks down what you can expect and how to confirm the correct plug size for your car.

Engine families and plug sizing

Most Mustang engines share a common thread size, but the reach and heat range vary by engine type. Below is a guide to what you can expect by engine family and how to verify the right plug size for your car.

• Thread diameter: 14 mm (approx. 0.551 inches). This is the standard thread size for the vast majority of modern Ford spark plugs used in Mustangs.


• Thread pitch: commonly 1.25 mm (M14x1.25). This is the typical pitch for 14 mm plugs in modern engines.


• Reach (threaded portion length): engine dependent, typically ranging from about 0.5 inches to 0.75 inches. The exact reach for your engine is specified by Ford in the owner's manual or service information.


• Heat range and plug type: range depends on engine and usage (regular street, performance, EcoBoost, etc.); OEM replacements from Ford/Motorcraft or approved brands will specify the correct heat range for your engine.

Concluding: For most Mustangs, you’re looking at a 14 mm spark plug with a 1.25 mm pitch, and the seating depth varies by engine. Always check the exact specification for your model year and engine code before replacing plugs.

How to confirm the exact size for your Mustang

To ensure you install the correct spark plugs, you should verify the exact size for your specific Mustang. Use these steps to confirm the right size:

1. Find your engine code and year in the vehicle documentation or on the engine label. The engine code determines the exact plug specification.


2. Consult Ford’s official parts catalog or the owner's manual for your model year to identify the OEM spark plug part number and size.


3. Inspect your current spark plugs: measure the thread diameter with a caliper, check the pitch if possible, and observe the total length of the threaded portion to estimate the correct reach.


4. When replacing, use OEM-designated plugs or reputable equivalents (e.g., Motorcraft, NGK, Denso) that match the specified thread size, reach, and heat range.

Concluding: By confirming the engine code and checking the OEM specification or current plug dimensions, you’ll ensure you choose the right spark plugs for your Mustang.

Notes for specific Mustang variants

5.0/5.2 Coyote V8 (2011–present)

These engines generally use 14 mm spark plugs with the appropriate reach per Ford's specification; the exact part number will be listed in the service information for your year. When in doubt, Ford Motorcraft plugs in the OEM recommended heat range are a reliable choice.

2.3L EcoBoost (2015–present)

EcoBoost Mustangs also use 14 mm spark plugs; verify the reach and heat range in the service information for your particular model year and engine code, since the EcoBoost configuration can require a different plug seating depth than the V8.

Summary

In short, most Mustangs use 14 mm spark plugs, with thread pitch typically 1.25 mm. The seating depth (reach) and heat range depend on the engine, so always confirm with the engine code and OEM specifications for your year and model to ensure correct size and performance. Using the correct plug helps maintain performance and avoid misfires or damage.

What size socket is a Mustang?

Includes a 13/16" (21mm) - 14mm socket size, right-hand 1.50 thread pitch.

What size socket for Mustang spark plugs?

Step 6: Install New Spark Plugs
Install the new spark plugs using a 9/16 inch deep socket or a 9/16 inch spark plug socket.

What socket size is used for spark plugs?

The most common spark plug socket sizes are 5/8 inch ($16$mm) and 13/16 inch ($18$mm), but other sizes like 9/16 inch and 14mm are also used. The correct size depends on your specific vehicle, and it's important to use the exact size to avoid damage, as using a standard socket instead of a spark plug socket can be problematic.
 
This video explains the different types and common sizes of spark plug sockets: 57sDanny Johnson’s GarageYouTube · Aug 7, 2025
Common spark plug socket sizes

• 5/85 / 85/8 inch ($16$mm): Very common for many smaller engines, new vehicles, and motorcycles. 
• 13/1613 / 1613/16 inch ($18$mm): Frequently used in some older Ford vehicles. 
• 9/169 / 169/16 inch: Used in some Ford vehicles and other applications. 
• $14$mm: A common metric size, especially in many newer European and Asian vehicles. 
• 3/43 / 43/4 inch ($18$mm): Used in some motorcycles, small engines, and older GM vehicles. 

What to consider when choosing a socket

• Vehicle-specific size: The best way to determine the correct size is to check your vehicle's owner's manual or the spark plug manufacturer's specifications for your engine. 
• Metric vs. standard: Make sure you use the correct type of socket. A standard socket may not fit a metric plug and vice-versa, and using the wrong one can cause damage. 
• Thin wall and 12-point: Some engines have tight spaces that require a specialized thin-wall socket, especially a thin-wall 12-point for certain European engines. 
• Spark plug sockets: These special sockets have an internal rubber insert or a magnetic grip to hold the plug securely in place as you remove or install it. 

This video shows the different types of spark plug sockets and how they work: 57sDanny Johnson’s GarageYouTube · Aug 3, 2025

What size socket is a Ford spark plug?

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.