What Size Socket Fits an Oil Drain Plug?

There isn’t a single universal size: most passenger vehicles use a metric socket between 13 mm and 19 mm for the oil drain plug, with 14 mm and 17 mm being the most common; on older U.S. vehicles you may find SAE sizes like 1/2″, 9/16″, or 5/8″. Some European models use internal hex (Allen) plugs—often 6 mm or 8 mm—and a few modern vehicles use Torx or quarter‑turn plastic plugs that don’t take a socket at all. The safest approach is to check your owner’s manual or measure the plug head before turning a wrench.

Why There Isn’t One Size for Every Vehicle

Automakers use different drain plug designs, driven by engine platform, oil pan material, and regional standards. Metric hex heads dominate modern cars globally, but thread size and head size vary by make and engine. Many European models use internal hex plugs that require a male Allen socket, and some newer vehicles use special plastic, quarter‑turn plugs designed to be replaced rather than torqued. Because head size isn’t the same as thread size—and even the same brand can mix designs—verification matters.

Common Socket Sizes by Brand and Vehicle Type

The following overview outlines typical oil drain plug head sizes seen in the field. Always verify your specific vehicle by consulting the owner’s manual, a reputable parts catalog, or by measuring across the flats of the plug head.

• Toyota/Lexus: commonly 14 mm external hex on many models.
• Honda/Acura: often 17 mm external hex (popular across many engines).
• Nissan/Infiniti: frequently 14 mm external hex.
• Subaru: commonly 17 mm external hex.
• Mazda: typically 14 mm or 17 mm external hex, depending on engine.
• Hyundai/Kia: often 17 mm external hex; some models use 14 mm.
• Ford (gas engines): commonly 13 mm or 15 mm external hex; some late‑model pans use a quarter‑turn plastic plug (no socket).
• GM/Chevrolet/Buick/GMC: usually 13 mm or 15 mm external hex on many trucks and cars.
• Chrysler/Dodge/Jeep/Ram: often 13 mm or 15 mm external hex; some engines vary.
• Volkswagen/Audi: frequently 19 mm external hex or 6 mm/8 mm internal hex (Allen), depending on engine.
• BMW/MINI: commonly 17 mm external hex or 8 mm internal hex on various engines; verify by engine code.
• Mercedes‑Benz: often 13 mm external hex or 8 mm internal hex; some use Torx on service plugs.
• Porsche: commonly 8 mm internal hex on many models (varies by engine).
• Motorcycles/powersports: typically 12 mm, 14 mm, or 17 mm external hex; some use internal hex.
• Small engines (mowers/generators): frequently 10 mm–14 mm external hex or square drive drain cocks.

These patterns cover a large share of vehicles but are not definitive. Head sizes can change across trims, model years, and updated oil pan or plug designs. When in doubt, confirm before loosening to avoid rounding the fastener.

How to Identify the Right Socket in Minutes

If your manual doesn’t specify the drain plug head size, you can quickly determine it with a few simple checks.

1. Check documentation: Look in the owner’s manual or a trusted parts catalog (by VIN) for the drain plug type and size.
2. Inspect the plug: Determine whether it’s an external hex, internal hex (Allen), Torx, square, or a quarter‑turn plastic plug.
3. Measure across flats: Use a caliper or a simple wrench/sizing gauge to measure the width of the hex head.
4. Test‑fit a 6‑point socket: Start with likely metric sizes (13, 14, 15, 17, 19 mm). It should fit snugly with no wobble.
5. Avoid adjustable wrenches: They can slip and round the head; use a proper socket and ratchet.
6. Select the right drive: A 3/8″‑drive ratchet handles most plugs; use a short extension if clearance is tight.
7. Note special cases: For internal hex, try 6 mm/8 mm Allen sockets; for Torx, T45/T50 are common. Quarter‑turn plastic plugs don’t use sockets and are typically replaced.
8. Prepare a new crush washer: Many plugs (especially Japanese brands) use a single‑use aluminum or copper washer—replace it to prevent leaks.
9. Torque correctly: Tighten to the factory spec with a torque wrench to avoid stripping threads (verify your vehicle’s spec).

Following these steps reduces the risk of damaging the plug or oil pan and ensures a proper seal after the oil change.

Tools and Tips for a Clean, Damage‑Free Oil Change

Best Socket Type and Drive

A 6‑point socket grips the flats of the plug better than a 12‑point and is less likely to round the fastener. Most jobs are comfortable with a 3/8″‑drive ratchet; a 1/2″‑drive is useful for large truck plugs. A shallow socket usually fits best; use a short extension for clearance around splash shields or skid plates.

Torque and Crush Washer Guidance

Always confirm the exact torque for your engine. As a general ballpark, many aluminum oil pans specify roughly 25–33 lb‑ft (34–45 N·m), while some steel pans and larger truck engines may call for around 30–40 lb‑ft (41–54 N·m). Replace the crush washer every oil change if your plug uses one (common thread sizes include M12 and M14 with corresponding washers). Over‑tightening is a major cause of stripped pans and leaks.

Special Cases to Watch

Some late‑model vehicles—particularly certain Ford and European applications—use plastic, quarter‑turn drain plugs intended for one‑time use; follow the service procedure and replace with a new plug rather than torquing a socket on them. Many European engines use internal hex (Allen) or Torx drains; make sure you have the correct bit before starting. Skid plates or undertrays may hide the plug—remove access panels as specified to avoid mess or damage.

Quick Reference: Typical Size Ranges You’ll Encounter

While you must verify your exact vehicle, these are the sizes most DIYers and technicians reach for first.

• Common metric external hex sockets: 13 mm, 14 mm, 15 mm, 17 mm, 19 mm.
• Common SAE external hex sockets (older U.S. models): 1/2″, 9/16″, 5/8″.
• Internal hex (Allen) bits often used on European models: 6 mm, 8 mm, 10 mm.
• Torx on certain plugs: typically T45 or T50 (verify before use).
• Non‑socket styles: quarter‑turn plastic plugs (replace, don’t torque); some small engines use square drains that accept a 3/8″ ratchet drive.

Keeping these sizes on hand covers the vast majority of vehicles, but always test fit and confirm the service procedure for your specific model.

Summary

Most oil drain plugs take a 13–19 mm metric socket—14 mm and 17 mm are especially common—while some older U.S. vehicles use 1/2″, 9/16″, or 5/8″. European models frequently use 6 mm or 8 mm internal hex, and a few late‑model vehicles use Torx or quarter‑turn plastic plugs. Verify your exact size via the manual or measurement, use a 6‑point socket and a torque wrench, and replace the crush washer if equipped to ensure a leak‑free service.