There isn't a single universal size for all Honda models. The oil drain plug washer (crush washer) is sized to fit the drain plug shank on your specific engine, most commonly around 12–14 mm inner diameter depending on whether the plug is M12 or M14.
In practice, the correct washer is the copper (or aluminum) crush gasket that seals between the drain plug and the oil pan. If you replace oil, you should replace the washer to maintain a proper seal. The exact size varies by model, year, and engine type, so consult the owner's manual or service manual for your vehicle, or measure the washer you remove and match it.
Understanding Honda drain plug washers
The drain plug washer sits between the drain plug and the oil pan and is typically a copper crush washer. It compresses to seal the threaded hole and prevent oil leaks. The inner diameter should accommodate the size of the drain plug shank, not the thread. Using the wrong size can cause leaks or damage the oil pan. Honda platforms vary between cars, motorcycles, and other equipment.
Common sizes by Honda platform
The following guide reflects typical patterns across popular Honda platforms. Always confirm with the specific manual for your model.
- Cars and SUVs: Many Honda car engines use an M14 drain plug, with a copper crush washer whose inner diameter is about 14 mm and outer diameter around 22–24 mm.
- Motorcycles and ATVs: Honda motorcycles commonly use M12 or M14 drain plugs. Washers typically have an inner diameter of 12–14 mm (depending on plug) and an outer diameter around 20–23 mm.
- Small engines and power equipment: Similar ranges apply, often around 12–14 mm inner diameter for the crush washer, with a corresponding outer diameter similar to the above.
Because there is variation by model and year, the exact size should be verified against the service manual or by measuring the existing washer before buying a replacement.
How to verify and replace the washer
To be certain you get the right washer, use these practical steps while performing an oil change or parts lookup.
- Check the owner's or service manual for the exact washer size or part number for your Honda model.
- Remove the old washer and measure its inner diameter with calipers or a precise ruler; compare to common sizes (about 12 mm or 14 mm ID).
- Bring the old washer or the drain plug shank diameter (the part that goes through the pan) to a parts counter to confirm the correct copper crush washer size.
- Keep a small stock of common sizes (12 mm and 14 mm ID) if you service a range of Honda products, and replace the washer with a new copper crush washer when you change oil.
Using the correct washer size helps ensure a proper seal and prevents leaks; reusing an old washer can compromise the seal and lead to oil loss.
Summary
Honda does not use a one-size-fits-all drain plug washer. The inner diameter generally aligns with the drain plug shank size (commonly 12 mm or 14 mm), with outer diameters around 20–24 mm. Always verify for your specific model via the manual or measurement, and replace the washer when you change the oil to maintain a reliable seal.