The oil drain plug on a Honda Ridgeline uses a 14mm hex-head plug and a copper crush washer sized for a 14mm drain hole.
For practical maintenance, you’ll replace the copper crush washer during every oil change. A typical replacement washer is designed for a 14mm drain plug, with an outer diameter around 22 mm and an inner diameter near 14 mm, and a thickness of about 1 mm. Always use a new washer to ensure a proper seal and prevent leaks.
Model-year consistency and notes
Honda Ridgeline models built around the 3.5-liter V6 engine (Gen 1: 2006–2014; Gen 2: 2017–present) generally follow the same drain plug size and washer arrangement. While part numbers can vary by market or trim, the 14mm hex-head drain plug and copper crush washer are standard for routine oil changes.
Replacing the washer during an oil change
During an oil change, drain the old oil, remove the drain plug, and discard the old copper washer. Fit a new copper crush washer onto the drain plug before reinstalling it. Thread the plug by hand, then tighten to the vehicle’s recommended torque value as specified in the owner’s or service manual. Using a new washer helps ensure a leak-free seal and avoids damage from a deformed washer.
Summary
In short, the Honda Ridgeline typically uses a 14mm hex-head oil drain plug with a copper crush washer sized for a 14mm drain hole (outer diameter about 22 mm). Replace the washer at every oil change and consult the owner’s manual for the exact torque specification and any year-specific notes.