What size is the oil drain bolt?

There isn’t a single universal size for oil drain bolts; the correct size depends on your vehicle’s make, model, and engine. Both the hex head you use to loosen the bolt and the bolt’s thread into the oil pan vary by design.

Understanding what “size” means in practice

When mechanics refer to an oil drain bolt’s size, they’re usually talking about two measurements: the hex head size (the size of wrench or socket needed to remove it) and the thread size (the diameter and pitch that screw into the oil pan). Some plugs require a specific washer or gasket, and the wrench size may be metric (e.g., 12mm, 14mm, 17mm) or even a standard bolt size in older vehicles. Always confirm against your vehicle’s manual and the exact plug installed on your oil pan.

Common sizes you might encounter

Here are typical ranges you may encounter in passenger cars and light trucks. The exact size for your vehicle should be confirmed in the owner’s manual or by checking the OEM drain plug.

• Hex head/socket sizes often seen: 12 mm, 14 mm, 17 mm. Some motorcycles and certain engines use other sizes, including 19 mm in older designs.


• Thread diameters and pitches commonly found are in the range from roughly M10x1.25 up to M22x1.5, with the most common for modern cars often around M12x1.25 to M14x1.5.

Because plug size is model-specific, the two most reliable references are the vehicle’s owner’s manual or a parts diagram from the manufacturer. If you don’t have the manual, an auto parts store can help identify the correct plug by year, make, model, and engine code.

How to determine the exact size for your vehicle

1. Locate the oil drain plug on the oil pan. If you can’t see it easily, consult the service manual or a repair guide for your vehicle’s layout.


2. Inspect the plug head to identify the wrench size and whether it’s a hex (12/14/17 mm) or a square/Allen type. If it’s difficult to tell, measure across flats with a ruler or calipers.


3. Remove the plug carefully and inspect the thread on the plug and the oil pan. Count threads or measure the diameter of the threaded portion to estimate the thread size and pitch.


4. Reference the OE part number if visible on the plug or search the vehicle’s VIN-based parts catalog to match the exact drain plug (some vehicles use a washer or crush washer that must be replaced).


5. Confirm the correct torque specification from the manual or a service bulletin and use the appropriate gasket or washer when reinstalling.

With the exact plug identified, you can purchase a replacement if needed. If you are unsure, bringing the old plug to an auto parts store can help match the size and thread exactly before purchasing.

Tips for replacement and maintenance

Using the correct drain plug size is essential for preventing leaks and ensuring reliable oil changes. Always replace worn washers, apply the correct torque, and use the manufacturer’s recommended oil grade and quantity. If you upgrade to a drain plug with a magnet or a different washer, verify compatibility with your oil pan and vehicle warranty.

Summary

The key takeaway is that oil drain bolt size is not universal. By checking the owner’s manual, comparing the plug’s head size, and examining the thread dimensions, you can determine the exact size for your engine. When in doubt, consult the dealer or a trusted repair manual, and bring or reference the vehicle’s exact year, make, model, and engine code to ensure a precise match. Accurate sizing helps prevent leaks and ensures a smooth oil-change process.

How do I know what size my oil drain plug is?

There is no single oil drain plug size, as it varies by vehicle. Common sizes are expressed in a thread size format like M12x1.75cap M 12 x 1.75𝑀12𝑥1.75 or M14−1.50cap M 14 minus 1.50𝑀14−1.50, and a corresponding wrench or socket size like 15mm15 m m15𝑚𝑚 or 18mm18 m m18𝑚𝑚. The best way to find your car's specific plug size is to check the owner's manual, measure the plug directly, or look up the parts for your vehicle's make and model.
 
Common sizes

• M12×1.75cap M 12 cross 1.75𝑀12×1.75: Often paired with a 15mm15 m m15𝑚𝑚 wrench head. 
• M14×1.50cap M 14 cross 1.50𝑀14×1.50: A common size, sometimes with a different head size. 
• M16×1.50cap M 16 cross 1.50𝑀16×1.50: Also found on some vehicles, typically with a 17mm17 m m17𝑚𝑚 head. 

How to find your specific size

1. Check your owner's manual: This is the most reliable source for your vehicle's specifications. 
2. Look up parts: Many auto parts websites have a lookup tool where you can enter your car's information to find the correct plug. 
3. Measure the existing plug:
   • Thread size: You can use a thread pitch gauge to measure the distance between threads (in millimeters or threads per inch). 
   • Head size: Measure the diameter of the head that the wrench fits onto. 
4. Consult the plug itself: Some replacement plugs may have the size stamped on them, but this is not always the case. 

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What size socket is the oil drain plug?

There is no single socket size for all oil drain plugs, as it varies by vehicle, but common metric sizes are 13mm, 14mm, 15mm, 17mm, and 19mm. To find the correct size, check your vehicle's owner's manual or a set of assorted metric sockets if unsure. 
This video shows how to use different tools to remove an oil drain plug: 1mOn The WorkbenchYouTube · Nov 1, 2024
Common sizes

• Metric: The most common sizes for passenger vehicles are between 13mm and 17mm. 
• SAE: Some older or specialty vehicles may use SAE (inch) sizes, which are often fractional (e.g., 3/8" or 1/2"). 
• Specialty: Some plugs might have a square opening, a hex (Allen/Allen key), or a Torx (star) shape instead of a traditional bolt head. 

How to find the right size

1. Check your owner's manual: This is the most reliable source for your specific car. 
2. Use a socket set: Start with common sizes like 13mm, 14mm, 15mm, and 17mm. A 6-point socket is best as it grips the bolt head more securely. 
3. Visit an auto parts store: You can tell them your vehicle's make and model, and they can look up the correct size. 
4. Try a universal set: If you frequently change the oil, consider buying a specialized oil drain plug socket set that includes common metric and SAE sizes. 

This video explains the importance of using the correct tool to remove an oil drain plug: 1mYour Home GarageYouTube · Nov 24, 2022

Are all oil drain bolts the same size?

There isn't one size that fits all cars. Go to the autoparts place and tell them what car you have and they will look it up for you. If the threads on the oil pan hole are stripped out you can get an oversized drain plug to fit in. That is common and the plugs will rethread the hole as it is screwed in.

What size is the most common oil plug?

Most cars use oil drain plugs between 13mm and 17mm, depending on the brand.