Denso 5318 Spark Plug

Denso Iridium Power Spark Plug 5318

Denso Iridium Power spark plug 5318 is built for drivers who want precise ignition performance from a compact iridium design. With a 0.4 mm iridium center electrode, this plug is engineered for efficient spark delivery and consistent combustion response in the ignition system.

Key Features

• Denso Iridium Power line for performance-focused secondary ignition service
• 0.4 mm iridium center electrode for a fine-tip spark design
• Tapercut and U-groove ground electrode tip design
• Nickel ground electrode core with copper center electrode core
• 5000 ohm resistance for ignition circuit compatibility
• Pre-gapped to 0.7 mm
• 14.00 mm thread diameter, 19.00 mm reach, flat seat
• 20.6 mm hex size and heat range 29

Product Details

The Iridium Power product line is Denso’s performance-oriented spark plug family, focused on a small-diameter iridium center electrode for strong spark concentration and stable ignition characteristics. Part number 5318 is also referenced as Denso IW29, which helps when cross-checking service information for ignition tune-up work on vehicles such as Honda Civic and Toyota Corolla applications where the correct plug specification matters.

This spark plug uses a copper core center electrode with an iridium tip and a nickel ground electrode core. The tapercut and U-groove ground design supports a focused spark path, while the flat seat, 14.00 mm thread diameter, and 19.00 mm reach make it important to match the OE-style plug specification exactly. For fitment-based searches, this is the type of spark plug buyers look for when replacing a Denso 5318 spark plug on Honda Civic or Toyota Corolla ignition service.

What It Is Used For

• Replacing worn spark plugs that cause rough idle
• Restoring weak ignition performance and misfire conditions
• Addressing hard starting related to plug wear
• Improving combustion consistency during routine tune-up service
• Matching the specified heat range and thread dimensions for service replacement

Installation Notes and Tips

Verify thread diameter, reach, seat type, and heat range before installation. Use the specified 0.7 mm pre-gap as a reference and confirm final gap against the vehicle service manual when required. Because this plug uses a flat seat and 19.00 mm reach, correct application matching is essential for proper sealing and combustion chamber clearance. Fits should be confirmed by engine code and service specification for Honda Civic and Toyota Corolla models before installation.

Quality Assurance

Denso manufactures the Iridium Power line with a fine-wire iridium center electrode and application-specific ignition specifications. Part number 5318 is built to the listed dimensions and electrical resistance for consistent service replacement, and the IW29 cross-reference helps verify the correct Denso application.