What size is the oil screw?

It depends on the vehicle or machine—there is no single “standard” oil screw (oil drain plug) size. For most passenger cars, common thread sizes include M14×1.5, M12×1.25, M12×1.5, and M16×1.5, while some older American applications may use 1/2-20 or 9/16-18. To give you the exact size, I’ll need the make, model, year, engine, and which oil screw you mean (engine, gearbox, differential, etc.). Below is a guide to help you identify it quickly and accurately.

Why the size varies

Manufacturers choose different thread diameters, pitches, head styles, and sealing methods to suit engine design, oil pan material, and service practices. Even within the same brand, sizes can differ by engine family and model year. The term “oil screw” can also refer to drain, fill, or level plugs in engines, gearboxes, and differentials—each often uses a different thread and head type.

Common oil screw sizes by application

The following list outlines sizes frequently encountered in real-world service. Treat them as common, not universal, and verify before ordering parts or tightening to spec.

• Passenger cars/light trucks (engine oil drain): M14×1.5, M12×1.25, M12×1.5, M16×1.5; occasional SAE UNF like 1/2-20 or 9/16-18 on older domestic models.
• Motorcycles/scooters (engine oil drain): Often M12×1.25 or M12×1.5; some use M14×1.5. Inspection/check bolts can be M10×1.25.
• Manual gearboxes/differentials (drain/fill/level): Commonly larger metric like M18×1.5 or M22×1.5, or a 1/2-inch square-drive plug (no hex head). Always confirm because fill and drain may differ.
• Small engines/lawn equipment: Frequently 3/8-18 NPT (tapered pipe) drain plugs or metric such as M10×1.25; designs vary widely by brand.
• Sealing method: Most metric drain plugs seal with a crush washer (aluminum or copper) sized to the thread (e.g., 12, 14, 16 mm). NPT pipe plugs typically seal with thread sealant rather than a washer.

These patterns cover a large share of the field, but exceptions exist. The safest approach is to check official documentation or measure the plug you have.

How to identify your exact size

Use the steps below to determine the correct thread diameter, pitch, and sealing method without guesswork.

1. Check the owner’s or service manual: Many list the drain plug size, washer size, and torque spec.
2. Look up the OEM part number: Search your VIN or model/engine code on the manufacturer’s parts site or a reputable online catalog; specs often accompany the part listing.
3. Measure your existing plug: With calipers, measure the thread’s major diameter (e.g., ~14 mm suggests M14; ~12 mm suggests M12). For imperial, you may see ~0.5 in (~12.7 mm) indicating 1/2-inch.
4. Determine thread pitch: Use a thread pitch gauge. Metric pitch is the distance between threads (e.g., 1.5 mm), while imperial is threads per inch (e.g., 20 TPI). In a pinch, measure 10 mm of thread and count crests to approximate metric pitch.
5. Identify sealing style: Flat shoulder with a washer = straight thread (metric/UNF). Tapered, conical threads (slightly wider at one end) typically indicate NPT and use sealant.
6. Match the washer: The crush washer’s inner diameter usually matches the thread diameter (12, 14, 16, 18–20 mm). Replacing it like-for-like confirms sizing and ensures a proper seal.
7. Ask a trusted parts counter: Bring the plug; they can read the pitch and size with gauges and match a replacement or magnetic version.

Confirming all three—diameter, pitch, and sealing method—prevents cross-threading, leaks, or overtightening damage.

Wrench and bit sizes you might encounter

The head or drive style can vary independently of the thread size. Here are the common tool interfaces you’ll see during oil service.

• External hex (socket/wrench): Common sizes include 12 mm, 13 mm, 14 mm, 17 mm, and 19 mm for metric plugs.
• Internal hex (Allen): Often 6 mm, 8 mm, or 10 mm on some gearboxes and European applications.
• Square-drive plugs: Many gearboxes/diffs take a 3/8-inch or 1/2-inch square-drive ratchet directly—no socket needed.
• Other: Less common Torx or large slotted plugs exist; verify before disassembly.

Matching the correct tool reduces the risk of rounding the head or damaging the plug, especially on soft aluminum pans or tight spaces.

Torque and washer guidance

Correct torque and a fresh washer are as important as the right thread size. Over-tightening can strip pans; under-tightening can leak.

• Typical torque ranges (always check your manual):
  – M12 plugs: about 25–35 N·m (18–26 lb-ft).
  – M14 plugs: about 30–45 N·m (22–33 lb-ft).
  – M16 plugs: about 35–50 N·m (26–37 lb-ft).
  Materials and gasket style can shift these values—follow OEM specs when available.
• Washers: Single-use aluminum or copper crush washers are standard for straight threads. Replace every oil change to ensure a reliable seal.
• NPT (tapered) threads: Use appropriate thread sealant or PTFE tape if specified; do not use crush washers. Tighten to spec—tapered threads can crack housings if overtightened.

When in doubt, default to the manufacturer’s torque spec and a new washer. A small torque wrench is a wise investment for routine oil changes.

What I need from you to answer precisely

If you want the exact oil screw size without measuring, share the details below and I’ll look it up in OEM documentation or reliable catalogs.

• Make, model, year, and engine or engine code (e.g., 2.0L turbo, V6).
• Which plug you mean: engine oil drain, gearbox drain/fill, differential drain/fill, or level screw.
• Any relevant submodel or drivetrain info (AWD/4×4, manual/automatic, trim).
• Photo of the plug or the old washer (helps confirm head type and sealing style).

With that information, I can provide the exact thread size, washer size, and torque spec for your application.

Summary

There’s no universal oil screw size: the correct thread and washer depend on the specific engine or gearbox. Common engine drain plug sizes include M14×1.5, M12×1.25, M12×1.5, and M16×1.5, with some older SAE UNF plugs in domestic vehicles. Verify via the manual, OEM part lookup, or by measuring diameter and pitch, and always use the proper washer and torque. Share your vehicle or equipment details, and I’ll pinpoint the exact size for you.

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.

What size tool do I need to change oil?

Ratchet and Socket Set
Get a set that includes some metric and SAE sizes, and if you’re starting out, a 3/8” drive should do just fine. Ratchets and sockets also come in 1/4, 1/2″, 3/4″, and 1” drives. Many medium sized kits will include ratchets and sockets in 3/8” and 1/2″ drive.

What size is the oil drain screw?

There is no universal size for an oil drain plug; the correct size depends on the vehicle’s make and model, but common thread sizes include M12, M14, and M16, with different thread pitches and specific bolt head sizes (e.g., 15mm or 17mm) that require different wrenches. To find the correct size for your vehicle, you must check your vehicle’s owner’s manual, consult an online parts catalog using your car’s specifics, or measure the bolt head and thread on the existing plug.
 
This video explains how to find the right drain plug size for your vehicle: 56sDeanin’ It YourselfYouTube · Apr 8, 2024
How to Find the Right Drain Plug Size

1. Consult Your Owner’s Manual: The most reliable source for the correct bolt size is your car’s owner’s manual. 
2. Use Online Parts Catalogs: Websites like RockAuto.com offer parts databases where you can enter your vehicle’s year, make, and model to find the correct specifications. 
3. Measure the Existing Bolt: 
   • Wrench Size (Bolt Head Size): Use the correct metric or imperial wrench to measure the head of the drain plug to avoid rounding it. Common sizes can be 15mm, 17mm, or 9/16″, but there’s no single standard. 
   • Thread Size: The drain plug’s thread size is given in an M-number (e.g., M12) followed by the pitch (e.g., 1.5). For example, a common specification is M12x1.5. 
4. Check the Replacement Plug: If you’re buying a new drain plug, check its specifications to ensure it matches the required size for your vehicle’s oil pan. 

Important Considerations

• Avoid Overtightening: Using the incorrect drain plug or overtightening it can strip the threads on the oil pan, which is a costly repair. 
• Use the Correct Gasket: Always use a new gasket when installing a drain plug, as it is essential for preventing oil leaks. 

What size socket is an oil filter?

There isn’t one single “oil filter socket size” as it varies by vehicle; common sizes include 32mm, 36mm, and 27mm for cartridge-style filter housings found on brands like BMW, VW, and GM. To determine the correct size, you must first identify the specific make and model of your vehicle or the oil filter itself and then purchase the corresponding socket or a specialized oil filter wrench set.
 
This video explains the different types of oil filter wrenches and how they are used: 43sYour Home GarageYouTube · Oct 11, 2021
How to Find the Correct Oil Filter Socket Size

1. Check Your Vehicle’s Manual: Opens in new tabYour owner’s manual will often specify the correct size filter and the corresponding tool for its replacement. 
2. Inspect the Oil Filter Housing: Opens in new tabLook for a size marking directly on the oil filter cap itself. 
3. Purchase a Tool Set: Opens in new tabMany auto part stores and online retailers sell oil filter socket or cap wrench sets that include several common sizes, such as 27mm, 32mm, 36mm, and more. 
4. Use a Universal Oil Filter Wrench: Opens in new tabFor spin-on type oil filters, you can use a universal wrench that grips the filter’s canister, rather than a socket that fits a cap. 

Common Sizes and Applications

• 32mm: Commonly used for oil and fuel filter caps on various GM, Volkswagen, Audi, and BMW vehicles. 
• 36mm: Often found on BMW, Ford, and Mercedes-Benz models. 
• 27mm: Used in some Mercedes-Benz and other applications.