What Size Is the Oil Drain Plug on an Audi A4?

Most modern Audi A4 models use an oil drain plug with an M14 x 1.5 thread size, typically requiring either a 19 mm or 17 mm hex socket for removal, but the exact size can vary by engine, model year, and whether the pan or plug has been replaced, so it’s essential to confirm for your specific vehicle before servicing.

Why the Oil Plug Size on an Audi A4 Isn’t One-Size-Fits-All

The Audi A4 has been produced across several generations with different engines—gasoline, diesel, and mild hybrid setups—so there isn’t a single universal drain plug size for every A4 ever built. While there are strong patterns (especially in recent models), the safest approach is to combine general guidance with a quick verification on your specific car using the VIN or a visual check.

Common Oil Drain Plug Sizes by Audi A4 Generation

Most owners want a quick reference to know which plug they likely have before buying tools or replacement parts. The following breakdown covers the most common sizes used on A4 models sold in the U.S. and Europe, but some regional variants and prior repairs may differ.

B6 & B7 Audi A4 (Approx. 2001–2008)

For the B6 and B7 generations, engine design and sump material dictated the plug style and size. These cars typically use a steel plug threading into an aluminum pan, making correct size and torque especially important to avoid stripping threads.

• Thread size (most 1.8T & 2.0T petrol, many 1.9 TDI/2.0 TDI): M14 x 1.5
• Head size: Usually 19 mm hex
• Common replacement bolt examples:
  

  • OEM-style steel drain plug, M14 x 1.5 with crush washer
  • Aftermarket “magnetic” M14 x 1.5 drains (head usually 19 mm)

• Washer type: Single-use aluminum or copper crush washer
• Typical torque spec: ~30 Nm (22 lb-ft) for M14 x 1.5 on aluminum pan (always confirm for your exact engine)

Across these years, Audi remained broadly consistent with the M14 x 1.5 thread, but plug head size and washer material could vary slightly between OEM suppliers and markets, so checking your plug visually before ordering parts is wise.

B8 & B8.5 Audi A4 (Approx. 2008–2016)

With the B8/B8.5 generation, the 2.0 TFSI/TSI engines became dominant, and Audi standardized many service components. Nonetheless, variations still exist depending on whether the engine uses a conventional metal pan or a composite design and whether it has been retrofitted.

• Primary engines: 2.0 TFSI / TSI petrol, 2.0 TDI diesel
• Most common thread size: M14 x 1.5
• Typical head size: 19 mm hex
• Some diesel variants: May use the same M14 x 1.5 plug but with a different OEM part number and washer style
• Aftermarket plugs: Often interchangeable across many VW/Audi models using M14 x 1.5

In practical terms, if you have a B8/B8.5 A4 with the 2.0 TFSI, an M14 x 1.5 plug that takes a 19 mm socket is overwhelmingly likely—but never assume if a previous owner may have changed the pan or plug style.

B9 Audi A4 (2017–Present)

The B9 generation brought more substantial changes in engine architecture and increasingly common use of plastic/composite oil pans on some variants. Many B9 A4s use a plastic screw-in drain plug instead of a traditional steel bolt with a crush washer.

• Common setup on 2.0 TFSI (U.S. & EU): Plastic drain plug with O-ring in a composite pan
• Typical thread size (plastic plug): Functionally equivalent to M14 x 1.5 range, but treated as a model-specific part rather than a generic metal bolt
• Head type: Usually internal hex (Allen) or Torx-style head
• Typical tool size: Often a 6 mm or 8 mm Allen/hex bit, or Torx (varies by exact part number)
• Replacement practice: Often specified as “replace every oil change” due to plastic construction and O‑ring sealing

For B9 models, knowing the generic “M14 x 1.5” spec is less helpful than simply buying the correct OEM-style plastic plug by part number, because attempting to use a metal plug in a composite pan can cause damage.

How to Confirm the Correct Oil Plug Size for Your Specific A4

Given the overlap between generations, engine codes, and potential prior repairs, direct confirmation is the best way to avoid buying the wrong plug or rounding out the head with an incorrect tool.

The following checks help you confidently identify the right size and part for your car before you start draining oil.

1. Check your owner’s manual: Some manuals list the drain plug specifications or at least the required sealing washer and torque spec, which can be cross-referenced to plug size.
2. Use your VIN with an online parts catalog: Sites that access Audi’s ETKA-style databases can show the exact drain plug and washer part numbers associated with your VIN, including whether it’s plastic or metal and its thread size.
3. Inspect the plug physically: Clean the plug head and measure:
   

   • Head size: Use a caliper or test sockets (e.g., 17 mm vs. 19 mm).
   • Thread diameter: M14 means approximately 14 mm outer thread diameter.
   • Thread pitch: M14 x 1.5 means threads are 1.5 mm apart; a thread gauge can confirm.

4. Look for markings: Some OEM plugs are stamped with “M14x1.5” or a part number that you can search.
5. Ask a dealer or independent Audi specialist: Providing your VIN and engine code (e.g., CAEB, BWT, CNCD) usually yields the exact plug and torque spec within minutes.

Taking a few minutes to verify your plug before buying tools or parts dramatically reduces the risk of stripping threads, cracking a plastic pan, or being stuck mid-service with the wrong replacement bolt.

Tools and Parts You’ll Typically Need

Once you know the correct plug type and size, having the right tools and consumables on hand will make the oil change straightforward and prevent damage to the sump or plug.

• Correct socket/bit: Usually 19 mm socket for older metal plugs; Allen or Torx bit for newer plastic plugs.
• Torque wrench: Essential to tighten to the specified Nm value and avoid overtightening.
• New drain plug (optional but recommended): Particularly on plastic plugs and on older metal ones that show wear or corrosion.
• New crush washer or O-ring: Replace every time to ensure a proper seal.
• Brake cleaner and rags: To clean the area around the plug and check for leaks afterward.

With the right plug, washer or O‑ring, and a properly calibrated torque wrench, an Audi A4 oil change becomes a controlled, repeatable task rather than a gamble that could damage the oil pan or cause leaks.

Risks of Using the Wrong Plug Size or Tool

Misjudging the plug size or using an ill-fitting tool can turn a routine oil change into an expensive repair, especially on aluminum or composite pans.

The main problems that arise from incorrect sizing or technique are mechanical and safety related.

• Stripped pan threads: Over-tightening or forcing a mismatched thread (e.g., wrong pitch) can strip the aluminum or plastic threads, often requiring a new pan or thread insert (helicoil) repair.
• Rounded plug head: Using the wrong socket size (e.g., a loose 18 mm on a 19 mm plug) can round off the head, making future removal very difficult.
• Leaks from improper sealing: Reusing old washers or O‑rings, or using a plug with the wrong seat profile, can cause slow leaks that may not be immediately visible.
• Cracked plastic pans or plugs: Exceeding torque specs on plastic components can cause hairline cracks, which often only show up later as persistent leaks.

Checking the correct plug type, thread, and head size before starting—and always tightening to spec with the proper tool—largely eliminates these risks and protects both the engine and your wallet.

Bottom Line: Typical Size, With Important Caveats

For many Audi A4 models, especially B6, B7, and B8 generations with steel plugs, the oil drain plug is an M14 x 1.5 bolt typically removed with a 19 mm socket. Newer B9 cars often use a model-specific plastic plug with an internal Torx or hex drive and O‑ring seal rather than a generic metal M14 bolt. Because parts can vary with engine code, market, and prior repairs, the most reliable method is to verify using your VIN and a visual check before purchasing a replacement or starting an oil change.

Summary

In practice, most Audi A4s use an M14 x 1.5 oil drain plug, usually with a 19 mm hex head on older metal designs and a model-specific plastic plug with an internal drive on newer B9 cars. However, this is not universal across every engine and year, and previous owners may have changed the pan or plug. To avoid stripped threads, leaks, or damaged plastic pans, always confirm your plug’s exact type and size via your VIN, a trusted parts catalog, or a visual inspection, and use the correct tool and torque when reinstalling.

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

What size is the oil drain plug on a 2014 Audi s4?

All right now we’re going to pull the drain plug it’s a 6 mm Allen. And let the oil drain. Oh no now we’re going to install our new drain plug and crush washer to 22 foot-lb.

What size is the drain plug on an Audi A4?

The Audi A4 oil drain plug is an M14-1.50 size. For older models, it can be a 14mm bolt, and the size can vary by year, so it’s best to confirm the specific size for your vehicle’s model year. 

• Thread size: M14-1.50 
• Head size: Varies by model year, but can be 19mm, 14mm, or a Torx bit 
• Important: Always confirm the specific size and tool needed for your A4’s model year, as it can vary. 

Can I put 5W-30 in my Audi A4?

Audi recommends using synthetic oil that meets the VW 502 00 specification. Here are a few top choices: Castrol EDGE 5W-30 Full Synthetic Motor Oil: Known for its exceptional strength under high pressure, this oil provides superior protection and performance for your Audi A4.