Denso 4155 Spark Plug

Denso 4155 U-Groove Spark Plug Overview

The Denso 4155 spark plug is part of the U-Groove Conventional line, built for drivers who want consistent ignition performance and OE-style fitment. Its U-groove electrode design is engineered to improve ignitability, which supports smoother combustion and more efficient engine operation.

For shoppers searching for a Denso spark plug for Honda Civic or other secondary ignition service applications, this part number 4155 combines a copper core center electrode with nickel tip materials and a multi-electrode ground design.

Key Features

• U-Groove Conventional design for improved spark exposure at the gap
• Multi-electrode ground configuration with two ground electrodes
• Copper core center electrode for stable heat transfer
• Nickel center and ground electrode tip materials
• 5000 ohm resistance for ignition system compatibility
• Pre-gapped at 0.7 mm
• 14.00 mm thread diameter, 19.00 mm reach, and flat seat type
• 16.0 mm hex size for standard service tool access
• Manufacturer heat range 27

Product Details

Denso 4155 is a conventional spark plug designed around a U-groove electrode profile that helps expose the spark kernel more effectively than a standard round-wire layout. The copper core center electrode supports heat dissipation, while the nickel electrode materials provide a durable firing surface for routine ignition service. This configuration is suited to drivers replacing worn plugs in vehicles that call for a 14 mm, flat-seat spark plug with a 19.00 mm reach. This part cross-references DENSO Auto Parts (e.g., U27ETR) for the same application.

For Honda Civic maintenance and other ignition tune-up work, part number 4155 is a practical OE-style replacement choice when the engine specification matches the listed dimensions and heat range. The Denso U-Groove Conventional line focuses on dependable ignition performance without unnecessary complexity.

Common Issues This Spark Plug Can Address

• Hard starting caused by worn or fouled spark plugs
• Rough idle from inconsistent spark delivery
• Misfire conditions related to degraded electrode surfaces
• Reduced fuel efficiency from incomplete combustion
• Weak acceleration caused by ignition wear

Installation Notes and Tips

Verify thread diameter, reach, seat type, and heat range against the vehicle service specification before installation. Use the correct spark plug socket for the 16.0 mm hex and inspect the ignition system, plug wires, and coil components during service. Check the gap only if the application requires adjustment, since this plug is pre-gapped at 0.7 mm.

Compatible With vehicles that specify this Denso 4155 configuration, including Honda Civic applications where the listed dimensions and heat range match the factory requirement.

Quality Assurance

Denso manufactures ignition components to OE-level dimensional and performance standards, and the U-Groove Conventional design reflects that focus on consistent spark delivery and engine efficiency. Always confirm the part number 4155 against the vehicle catalog before installation.