NGK 4055 Spark Plug

NGK Iridium IX Spark Plug 4055 Overview

NGK Iridium IX Spark Plug 4055 is built for precise ignition performance in a wide range of import and performance applications. With an iridium center electrode, copper core, and 5000 ohm resistance, it supports stable spark delivery and consistent combustion in vehicles such as the Mitsubishi Lancer, Porsche 911, and Honda Civic.

The NGK Iridium IX Spark Plug line focuses on durable electrode construction and OE-level manufacturing standards. Part number 4055 is a direct-reference spark plug for applications that call for a 14 mm thread, flat seat, 0.75 inch reach, and a pre-gap of .032 inches, with application-specific gap settings noted in the fitment data.

Key Features

• Iridium tip material for the center electrode
• Copper core center electrode for efficient heat transfer
• Nickel ground electrode with taper cut tip design
• 5000 ohm resistance for ignition system compatibility
• 14 mm thread diameter, 13/16 hex size, flat seat
• Manufacturer heat range 7
• Pre-gapped at .032 inches; verify vehicle-specific gap requirements before installation
• Part number 4055 / BPR7EIX

Detailed Description

NGK 4055 is an Iridium IX spark plug engineered for vehicles that require a fine-wire iridium center electrode and a standard ground configuration. The iridium tip helps maintain sharp spark focus, while the copper core supports thermal control under demanding operating conditions. This combination is well suited to older and performance-oriented engines that rely on accurate ignition timing and consistent plug performance.

Compatible With applications include 2003-2005 Mitsubishi Lancer, 1980-1983 Porsche 911, 1978-1979 Honda Civic, 1983-1986 Audi Quattro, and 1954-1959 Mercedes-Benz 300SL. The part number 4055 also appears in fitment for select Maserati, Dodge, Chrysler, Ferrari, Lamborghini, and Mitsubishi models, making it a useful reference for long-tail searches such as NGK 4055 spark plug for Mitsubishi Lancer, NGK BPR7EIX for Porsche 911, and NGK Iridium IX for Honda Civic.

This part cross-references DENSO Auto Parts 5307 for the same application.

What It Helps Address

• Hard starting caused by worn or inconsistent spark plugs
• Misfire conditions related to degraded electrode performance
• Rough idle from weak or unstable ignition output
• Reduced throttle response from inefficient combustion
• Maintenance replacement for vehicles calling for NGK BPR7EIX / 4055

Installation Notes and Tips

Confirm the vehicle’s specified spark plug gap before installation. Fitment notes call for different gap settings by application, including 0.028, 0.032, 0.044, 0.025, and 0.024 inches depending on the vehicle. Use the correct torque procedure for the cylinder head material, and verify the 14 mm thread, 0.75 inch reach, and flat seat match the engine specification before tightening.

For vehicles such as the Mitsubishi Lancer, Porsche 911, and Honda Civic, follow the factory service information for gap and torque settings to maintain proper ignition performance.

Quality Assurance

NGK is a major OE spark plug supplier in North America with decades of automotive manufacturing experience. Part number 4055 is produced to support original-equipment standards for durability and operational consistency across domestic and import applications.