Denso 4065 Spark Plug

Denso 4065 U-Groove Conventional Spark Plug

The Denso 4065 spark plug is built to OEM quality standards for dependable secondary ignition performance. As part of the Denso U-Groove Conventional line, it uses a copper core center electrode, nickel tip materials, and a standard ground electrode layout to support consistent spark delivery in the correct heat range.

Key Features

• Denso U-Groove Conventional spark plug for OEM-style replacement service
• Part number 4065, also referenced as Denso W31FS
• Standard ground electrode design with one ground electrode
• Copper core center electrode for stable heat transfer
• Nickel center and ground electrode tip materials
• Pre-gapped to 0.7 mm
• 14.00 mm thread diameter, 12.70 mm reach, flat seat
• Manufacturer heat range 31
• 20.6 mm hex size for proper socket fit

Product Details

The Denso U-Groove Conventional line is focused on straightforward OE-style ignition service, and this spark plug follows that approach with a standard ground configuration and a nickel-tipped electrode design. The copper core helps manage heat transfer, while the 0.7 mm pre-gap supports correct ignition setup out of the box. For drivers searching for a Denso 4065 spark plug, Denso W31FS replacement, or an OEM-quality spark plug for secondary ignition service, this part provides the core specifications needed for accurate replacement work. It is a direct-fit style spark plug for applications that call for the listed thread diameter, reach, seat type, and heat range.

This part cross-references Denso Auto Parts (e.g., W31FS) for the same application.

What It Helps Address

• Misfires caused by worn or eroded spark plug electrodes
• Hard starting related to weak ignition spark
• Rough idle from inconsistent combustion
• Reduced throttle response from degraded plug performance
• Service replacement needs for vehicles using the specified Denso 4065 configuration

Installation Notes and Tips

Verify the thread diameter, 12.70 mm reach, flat seat, and 20.6 mm hex size before installation. Check the gap against the engine specification even though the plug is pre-gapped to 0.7 mm, and install only in engines that call for the listed heat range and electrode configuration. For vehicle-specific searches, use terms such as Denso 4065 spark plug for Honda Civic, Denso 4065 spark plug for Toyota Corolla, and Denso W31FS replacement spark plug when confirming the correct application.

Quality Assurance

Denso manufactures this spark plug to OEM quality standards for consistent replacement service. The U-Groove Conventional design reflects Denso’s conventional ignition component lineup, with materials and dimensions selected to match the listed specifications for accurate fitment and dependable operation.