What Is The Thread Size Of A Spark Plug

Are you a car enthusiast or do you just want to know how your car works from the inside out? If so, you may have questioned what a spark plug’s thread size was. Although the thread size may appear to be a minor and unimportant aspect, it is vital to the longevity and optimal efficiency of your engine. This blog will go into the subject of spark plugs and examine what is the thread size of a spark plug. So fasten your seatbelts because we’re ready to solve this intriguing vehicle mystery!

How to Measure Spark Plug Thread Size

Incorrect sizing can lead to poor fitment and possible engine damage. Here are 5 methods for measuring spark plug thread size that guarantee accuracy.

1. Pitch Gauge: 

You can precisely gauge the space between threads using this useful tool. Simply align the measurement on the gauge with the threads of the spark plug using the pitch gauge.

2. Calipers:

 You can measure the diameter of the threaded portion of a spark plug more precisely with a set of calipers. Read off the measurements after tightly wrapping the calipers around one of the threads.

3. Thread Checker: 

For precisely measuring thread sizes, a thread checker or thread pitch gauge is created. Check each component of your spark plug against the various thread-checking instruments in your collection until you find a perfect match.

4. Vernier Scale: 

A vernier scale, which functions similarly to calipers but offers even better accuracy in reading measurements down to small increments, is an option for individuals who prefer analog measuring equipment.

5. Consult Manufacturer Specifications:

 A second surefire technique is to accurately determine the type and size of spark plugs that the manufacturer of your car or spark plugs recommends for their engines by consulting their specifications online or in a user manual.

SizeMajor Diameter
Minor Diameter1)
Tap Drill
M10 x – 8.9171.009.2065
M12 x 1.2512.010.912 – 10.6471.2510.972
M14 x 1.2514.012.912 – 12.6471.2512.9072
M18 x 1.518.016.676 – 16.3761.5016.7568
Spark Plug Thread Size Chart (Source)

What Are Some Common Thread Sizes For Spark Plugs?

How nicely the spark plug fits into the engine’s cylinder head is determined by using the thread length. Spark plug threads usually have diameters of 10mm, 12mm, and 14mm. Modern vehicles commonly have a 14mm thread diameter.

It’s widespread don’t forget that variations exist even within these usual sizes. Pitch, which describes the distance between every thread ridge, can vary for a 14mm spark plug, for example, from 1.25mm to 1.5mm.

Depending on the engine architecture and specs wished for optimum performance, many motors require specific thread sizes. Always make certain to select a spark plug with the right thread diameter and pitch for your specific car model with the aid of consulting your proprietor’s handbook or getting expert guidance.

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Factors To Consider When Choosing A Thread Size

1. Material Strength: 

When selecting a thread size is the strength of the material being threaded. Using a bigger thread size can jeopardize the integrity of a weak material. On the other side, a weak material with a lower thread size may have stripped or broken threads.

2. Load Capacity: 

The thread duration needs to also be decided through the maximum load excellently to be completed to the threaded joint. For greater weights, a larger thread is probably required to make sure it has good enough strength and longevity.

3. Space Constraints: 

When selecting a thread size, take the available region for threading under consideration. When the area is at a top rate, deciding on a smaller thread would possibly help fit tight locations without sacrificing performance.

4. Application Type: 

Thread energy and precision necessities range depending on the application. Depending on the wishes of your software program, decide whether best or coarse threads are required.

5. Environmental Aspects: 

It’s additionally crucial to recollect the surroundings wherein the threaded joint will be characteristic. When deciding on the suitable thread length that can undergo those situations, recollect factors like temperature extremes, exposure to moisture or chemical compounds, and vibration ranges.

6. Compatibility with Existing Threads: 

Compatibility with gift threads becomes essential when inclusive of or replacing threaded components in a gift system to guarantee correct wholesome and functionality.

7. Thread Engagement Length: 

The threads’ strength and resistance to losing under load or vibration depend on how tightly they are mated. Although larger thread sizes are required, longer engagement lengths typically offer better security.

Related:- What causes a spark plug to blow out

What is the thread size of a Ford F150 spark plug?

When changing spark plugs on a Ford F150, the thread size is a crucial aspect to take into account. The majority of models from 2004 and after suit the 14mm thread size, which is the most popular thread size for F150 spark plugs. To ensure accuracy, you must, however, refer to the owner’s manual for your particular car or seek advice from a reputable mechanic.

Having the correct thread size is crucial because it guarantees a suitable fit between the spark plug and the cylinder head. Poor combustion decreases engine performance, and even engine damage can result from a loose or mismatched thread. 


When installing or changing spark plugs in an engine, the thread size of every plug has to be taken into consideration. It decides if the plug will paint with and fit the cylinder head. To affirm the proper spark plug is used, check the proprietor’s manual or a dependable mechanic as one-of-a-kind motors and engines require various thread sizes.

Using the wrong thread length might result in subpar performance, engine harm, or maybe total failure. Therefore, for fine engine performance and lifetime, it’s miles critical to exactly discover and select the proper thread size in your spark plugs. So make sure to verify the thread size again the subsequent time you need to alternate your spark plugs!


What is the thread size of a d16 champion spark plug?

The thread size of a D16 Champion spark plug is 14mm. This refers to the diameter of the threads on the spark plug and is a standard size used for many types of engines. 14mm thread plugs are commonly found in cars, motorcycles, and small engines.

Are spark plug threads widespread?

No, spark plug threads are not typical, and also you must not use different sizes than the manufacturing facility-endorsed thread size.

Can I use any spark plug?

As long as you operate spark plugs with precise dimensions and warmth range, you may use spark plugs from exclusive manufacturers interchangeably without any trouble.

What occurs if I use the incorrect spark plug?

In case you have hooked up the wrong spark plug, it will cause constant rattling and knocking noises from the engine. If the vehicle feels jerky and disjointed, the chances are that your spark plugs aren’t working well. It additionally dangers detrimental to the engine as it might pre-ignite and misfire, putting strain on the engine.

Can I use WD40 on spark plugs?

Yes, the use of WD-forty in your spark plugs facilitates repelling water and protects them from corrosion as moisture is averted.

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