What size is the thread on a Subaru?

There isn’t a single universal thread size for Subarus—the size depends on the component (spark plugs, lug nuts, oil drains, etc.) and the model year.

For drivers and DIYers, knowing the typical ranges can help avoid buying the wrong parts. This article lays out common sizes and how to verify them for your specific Subaru.

Common thread sizes by component

Below are the thread sizes you’re most likely to encounter on many modern Subaru models. Always verify against your exact year and engine family before purchasing parts.

Spark plugs

Most Subaru engines (including many EJ/FA/FB families) use spark plugs with a 14 mm thread diameter and a 1.25 mm (0.049 in) thread pitch. Some older or specialized engines may differ, so confirm the exact plug size from your service manual or OEM part numbers for your engine.

Wheel lug nuts and wheel studs

Many Subaru models use metric wheel hardware with a common thread of M12 x 1.25 for lug nuts. The lug nut seat type and the specific socket size can vary by wheel design and year, so check your vehicle’s wheel specification or owner’s manual for the exact requirement.

Oil drain plugs

Oil drain plugs on a large portion of Subaru engines are commonly around M14 x 1.5, but some models and engine families may use different sizes (including M12 variants). Verify with your owner’s manual or the service bulletin for your exact engine family (EJ, FA, FB, etc.).

In short, the thread size you need depends on the component you’re servicing and the model year. Use the guidance above as a starting point, but always confirm for your specific car.

How to verify the correct size for your Subaru

To ensure you’re getting the right thread size, follow these steps before buying replacement parts or attempting repairs.

1. Check the owner’s manual or factory service manual for your exact model year and engine family to locate the correct thread specifications.


2. Look up the official Subaru parts catalog or dealer information for your VIN to confirm exact thread size for the component you’re working on.


3. Physically measure when possible: use a thread gauge or calipers to determine diameter and pitch, or bring the existing fastener to a parts counter for confirmation.


4. When replacing damaged threads, consider rethreading or using a helicoil or thread insert with professional installation, following the manufacturer’s torque specs.

If you’re unsure or dealing with a rare or older model, contacting a Subaru dealer or a qualified mechanic can prevent mismatches and potential damage.

Summary

Subaru thread sizes are not universal and vary by component and model year. Key patterns to remember are: spark plugs commonly use 14 mm threads with a 1.25 pitch, wheel lug nuts often use M12 x 1.25, and oil drain plugs are typically around M14 x 1.5, with variations by engine family. Always verify against your specific car’s manuals or official parts catalogs to ensure the correct size for maintenance and repairs.

What size socket for Subaru lug nuts?

The correct socket size for most Subaru lug nuts is 19mm (3/4"). While most Subarus use this size, it's crucial to use a high-quality, thin-wall, 6-point socket designed for automotive use to avoid damaging the lug nuts or wheel. 
Details to consider

• Standard size: The most common lug nut size is M12x1.25, which requires a 19mm socket. 
• Avoid damage: Using an undersized socket can strip the nut, while an oversized one can cause it to slip. A 6-point socket is recommended over a 12-point socket to prevent rounding the corners. 
• Specialty sockets: Some aftermarket lug nuts may have special shapes, like spline drives, which require a specific key socket. 
• Older models: Some older Subaru models might require a different size, such as a 21mm socket for those with a 14mm lug nut, but this is rare. 
• Protect your wheels: If you have alloy wheels, consider using a thin-wall impact socket or a socket with a protective sleeve to prevent scratching the finish. 

What size thread are Subaru wheel studs?

Subaru wheel studs have a M12x1.25 thread pitch, meaning they have a 12mm diameter and a 1.25mm pitch between the threads. This is a finer thread pitch than many other Japanese manufacturers, which often use a 1.5 pitch. 
You can watch this video to learn how to find the thread pitch for your car's wheel studs: 46sCar Performance ProsYouTube · Jun 18, 2025

• M12: The "12" refers to the nominal diameter of the stud in millimeters. 
• 1.25: The "1.25" is the thread pitch, indicating that the distance between each thread peak is 1.25mm. 
• OEM compatibility: This standard is consistent across most Subaru models for the last several decades, from the Impreza and Forester to the Legacy and Crosstrek. 
• Aftermarket considerations: When buying replacement parts like lug nuts or studs, it is crucial to confirm the M12x1.25 size to ensure proper fitment, as many other aftermarket parts may use a different pitch, like M12x1.5. 

This video explains the importance of using the correct thread pitch and how to check the length for thread engagement: 1mSubiSpeedYouTube · Jan 28, 2020

What thread pitch does Subaru use?

For example, the most common metric thread sizes of Subaru bolts are M12x1. 25mm. A M12 means the width of the thread area and a 1.25mm means the thread pitch. It is usually measured in millimeters.

What size is the drain plug on a Subaru?

Subaru oil drain plug sizes vary by model and year, but commonly use either a 14mm or 17mm socket. Some older models may use 9/16 inch, and the thread size is often M16-1.50, though this can differ. It is best to confirm the exact size for your specific vehicle by checking the owner's manual or using the correct socket on the plug.
 
Common Subaru drain plug sizes

• 14mm socket: Frequently used on newer Subaru models like the Crosstrek and some Foresters, notes Advance Auto Parts and eBay. 
• 17mm socket: A common size on older models, such as some 2015 Outbacks, says Reddit users, and is often the factory-installed size. 
• 9/16 inch: Some users report this size for specific models like a 2015 Outback, but it may be less common and is an inch-based measurement. 

How to confirm the correct size

• Check your owner's manual: This is the most reliable source of information for your specific vehicle.
• Test the socket: Try a 14mm and 17mm socket to see which one fits without excessive play. A 6-point socket is recommended to prevent stripping. 
• Measure the existing plug: If possible, you can measure the head of the plug to get the correct size.