What size are oil drain plugs?

Most modern passenger vehicles use metric drain plugs, with M14×1.5 being the single most common size; other frequent sizes include M12×1.25, M12×1.5, M14×1.25, and occasionally M16×1.5 or M18×1.5 on larger engines. The wrench size that fits the plug head is different from the thread size and typically ranges from 13–19 mm for hex heads. While many newer American, European, and Asian cars are metric, some older U.S. vehicles and small engines may use SAE or tapered pipe threads (for example, 1/2″-20 UNF or 3/8″-18 NPT). Always verify with the owner’s manual or an OEM parts catalog for your exact model and year.

What “size” really means on a drain plug

When people ask about drain plug size, they usually mean the thread specification: the outer thread diameter and its pitch (distance between threads). For example, M14×1.5 means a 14 mm thread diameter with a 1.5 mm thread pitch. This is not the same as the wrench or socket size needed to turn the plug (the hex head), which varies by design. The sealing interface also matters: many plugs seal with a crush washer whose inner diameter matches the thread size, while others use an O-ring integrated into the plug.

Common drain plug thread sizes

The following list highlights the drain plug thread sizes most frequently encountered on passenger vehicles today, plus a few examples seen on older vehicles and small engines. Use it as a reference point, not a substitute for model-specific confirmation.

• M12×1.25 — Common on smaller engines; often paired with a 12 mm crush washer.
• M12×1.5 — Also common; found across various compact and mid-size cars.
• M14×1.25 — Less common than 1.5 pitch but used by some manufacturers.
• M14×1.5 — Very common across many makes and models; often uses a 14 mm crush washer.
• M16×1.5 — Seen on some larger-displacement engines and trucks/SUVs.
• M18×1.5 — Used on certain trucks, SUVs, and performance or diesel applications.
• 1/2″-20 UNF (SAE) — Found on some older American vehicles and aftermarket pans.
• 3/8″-18 NPT (tapered pipe) — Seen on some small engines, power equipment, and a few legacy designs; seals on the taper, typically with thread sealant rather than a crush washer.

These sizes cover the majority of on-road applications. However, there are exceptions, including larger threads (e.g., M20) on certain performance and diesel engines, as well as manufacturer-specific designs. Confirm the exact spec before purchasing a replacement plug or washer.

Typical wrench and bit sizes used on drain plugs

Even when the thread is metric, the plug head (what your tool grips) can be metric, SAE, hex, internal Allen, Torx, or even square. The following are commonly used head/bit sizes; select based on what’s on your plug.

• Hex heads (metric): 13 mm, 14 mm, 15 mm, 17 mm, 19 mm.
• Hex heads (SAE): 1/2″, 9/16″, 5/8″ on some older or aftermarket plugs.
• Internal hex (Allen): 6 mm, 8 mm are common.
• Torx/Star: T45, T50 on some European applications and plastic/composite plugs.
• Square drive: Some plugs accept a 3/8″ or 1/2″ square ratchet directly.

Choose a tool that fits snugly to avoid rounding the plug, and replace the sealing washer or O-ring if the design calls for it. If the head looks unusual (plastic, Torx, or flush-mount), check the service procedure before removal.

Torque ranges and sealing washers

Drain plugs are easy to overtighten, especially in aluminum pans. When manufacturer torque specs are unavailable, these general ranges can help—but treating them as guidelines, not rules, is crucial. Replace crush washers or O-rings as specified to ensure proper sealing at the correct torque.

• M12 plugs: typically 20–25 N·m (15–18 lb-ft).
• M14 plugs: typically 25–35 N·m (18–26 lb-ft).
• M16–M18 plugs: typically 30–40 N·m (22–30 lb-ft).
• NPT/tapered plugs: tightened “snug” plus about 1/8–1/4 turn; sealing relies on the taper and thread sealant, not a crush washer.
• Sealing washers: copper or aluminum crush washers are most common; fiber and composite washers are also used. Match the washer’s inner diameter to the plug thread (e.g., 12 mm washer for M12, 14 mm for M14).

If the plug continues to seep after correct torque with a new washer, inspect the mating surface for scratches, replace the washer type with the OEM-specified material, or replace the plug. Avoid reusing aluminum crush washers, which deform permanently.

How to identify your exact drain plug size

To avoid guesswork and potential damage, follow a systematic approach to confirm your drain plug’s thread and sealing method before buying parts or reinstalling after an oil change.

1. Check official sources: your owner’s manual, the factory service manual, or an OEM parts catalog using your VIN.
2. Inspect the current plug: look for markings (e.g., M14×1.5) and note whether it uses a crush washer or O-ring.
3. Measure the thread: use calipers to check outer diameter (e.g., ~14.0 mm for M14), and a thread gauge to determine pitch (1.25 vs 1.5 mm). For SAE, count threads per inch.
4. Test-fit with known hardware: a matching nut or thread checker can confirm size without forcing the plug.
5. Identify thread type: parallel (metric/UNF) vs tapered (NPT). Tapered threads grow tighter as they seat; they usually require sealant, not a washer.
6. Match the washer: select the correct inner diameter and material specified by the OEM.
7. When in doubt: bring the plug to a parts counter with a thread gauge block, or consult a dealer with your VIN.

This process minimizes the risk of cross-threading, leaks, or stripped oil pans—especially important on aluminum pans, which are more susceptible to damage.

Special cases to know about

Not every vehicle uses a conventional metal hex-head drain plug. Some designs and situations call for different parts or procedures.

• One-time-use plastic/composite plugs with O-rings (seen on some European and late-model vehicles) must be replaced at each oil change.
• Aftermarket drain valves (e.g., quick-drain types) are sized to the factory thread (commonly M14×1.5) and include their own sealing method.
• Oversize “repair” plugs exist for stripped pans, but thread inserts (Heli-Coil/Time-Sert) are a more durable fix.
• Motorcycles and powersports often use M12 or M14 plugs, sometimes more than one drain; torque specs are typically lower.
• Heavy-duty trucks and diesels may use larger threads (e.g., M20 and above) and higher torque values.
• Small engines and lawn equipment frequently use NPT tapered plugs or drain bolts integrated into the crankcase.

If your vehicle falls into one of these categories, follow the manufacturer’s service procedure closely and use the specified replacement parts to ensure a reliable seal.

Summary

For most cars, the oil drain plug is metric, with M14×1.5 the most common; M12 and larger M16/M18 sizes also appear depending on engine and application. The head’s wrench size (often 13–19 mm) is not the thread size, and sealing is typically via a crush washer or O-ring. Use the owner’s manual or an OEM parts lookup to confirm the exact thread and washer, torque to spec, and replace single-use washers or plugs as directed to prevent leaks and pan damage.

What socket size do I need for an oil change?

You need a socket wrench (14mm or 15mm), an oil filter wrench, an oil drain pan, a funnel, and a new oil filter.

Are most oil drain plugs 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 socket fits an oil drain plug?

There isn’t a single socket size for all oil plugs; the correct size depends on your vehicle’s make, model, and year. Common sizes include 17mm and 14mm for many Japanese and European cars, but you might need to check your vehicle’s specifications or visit an auto parts store for help. A 6-point socket is recommended for better grip to avoid stripping the bolt head. 
How to find the right socket size

1. Check your vehicle’s manual: The most reliable way is to consult your car’s owner’s manual to find the specific drain plug size. 
2. Identify the head type: Most drain plugs have a hex-shaped bolt head. 
3. Measure the bolt head: If you have a socket set, try a few sizes to see which one fits snugly. 
4. Consult an auto parts store: Bring the vehicle information to an auto parts store, and they can look up the specific size for you. 
5. Consider common sizes: While not universal, many Japanese and European cars use metric sizes, with 17mm and 14mm being common. 

Tips for changing the oil plug

• Use a 6-point socket: This type of socket is more effective at gripping the bolt and prevents the head from getting rounded off. 
• Use a 3/8-inch drive socket and ratchet: This is a common size for most DIY oil changes. 
• Have a replacement plug ready: If the old drain plug is worn or stripped, you’ll need a new one to replace it. 

What size is a standard oil drain plug?

There is no single “standard size” for an oil drain plug, as sizes vary by vehicle make and model. To find the correct size, you need to check your vehicle’s owner’s manual or measure your existing plug’s thread diameter (e.g., M12, M14) and the required wrench size for the head (e.g., 15mm, 17mm).
 
How to Determine Your Drain Plug Size

1. Check Your Owner’s Manual: This is the best first step to find the correct size specified for your vehicle. 
2. Measure Your Existing Plug:
   • Thread Diameter: Measure the widest part of the plug’s threads to get the metric (M) or standard (SAE) diameter (e.g., M12 means a 12mm thread diameter). 
   • Head Size: The head size (e.g., 17mm) is the measurement needed for the wrench or socket you’ll use to remove and install the plug. 
3. Use a Vehicle-Specific Parts Catalog: Websites for auto parts stores or manufacturers like Dorman Products and NAPA Auto Parts have tools to help you find the right drain plug by entering your vehicle’s year, make, and model. 

Common Size Examples
While not standard, here are some examples of common sizes: 

• Metric: M12 x 1.5, M12 x 1.75, M14 x 1.50.
• SAE (Imperial): 1/2-20.