Denso 5366 Spark Plug

Denso Iridium Power Spark Plug 5366

Denso Iridium Power 5366 is a performance-focused spark plug built for precise ignition and stable combustion. It uses a 0.4 mm iridium center electrode, a copper core center electrode, and a nickel ground electrode to support consistent spark delivery in demanding engine conditions.

For drivers searching for a Denso spark plug for Honda Civic, Toyota Corolla, or similar import applications, this plug is part of the Iridium Power line and is engineered around compact electrode design and OE-style fitment dimensions.

Key Features

• Iridium center electrode with a 0.4 mm tip for concentrated spark delivery
• Tapercut and U-groove ground electrode tip design
• Slant ground configuration with one ground electrode
• 5000 ohm resistance for ignition system compatibility
• Pre-gap size: 0.9 mm
• 14.00 mm thread diameter, 19.00 mm reach, flat seat
• 16.0 mm hex size for standard service tool access
• Manufacturer heat range: 27

Iridium Power Line Details

The Denso Iridium Power line is built around fine-wire iridium technology for sharper ignition response and efficient spark concentration. Part number 5366 follows that design approach with a small-diameter center electrode and a ground electrode profile shaped to support reliable flame initiation in modern gasoline engines.

Detailed Description

Denso 5366 is a secondary ignition spark plug intended for engines that require a 14 mm thread, 19 mm reach, flat seat, and 0.9 mm pre-gap. The copper core center electrode helps manage heat transfer, while the iridium tip supports long-term electrode precision. This makes it a practical choice for maintenance on import vehicles where exact plug dimensions matter. If you are replacing worn plugs in a Honda Civic, Toyota Corolla, or another application that calls for this specification, Denso 5366 provides the correct physical profile and ignition-focused electrode design.

This part cross-references DENSO Auto Parts IU27A 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
• Maintenance replacement for engines requiring the listed thread, reach, and seat dimensions

Installation Notes and Tips

Verify the engine calls for a 14.00 mm thread diameter, 19.00 mm reach, flat seat, and 0.9 mm pre-gap before installation. Check the ignition system specification for 5000 ohm resistance and confirm the heat range matches the engine application. Use the correct 16.0 mm spark plug socket and follow the vehicle service manual for torque and gap verification. For Honda Civic, Toyota Corolla, and other import applications, confirm the OE plug specification before replacing the original part.

Quality Assurance

Denso manufactures the Iridium Power line with fine-wire iridium center electrode technology and application-specific dimensions for ignition service. Part number 5366 is built to the listed specifications for consistent fit and function in the intended engine applications.