NGK 91784 Spark Plug

NGK Ruthenium HX Spark Plug for OE-Style Ignition Performance

The NGK Ruthenium HX High Ignitability Spark Plug, part number 91784, is built for drivers who want precise ignition performance and dependable OE-style fitment. It uses a ruthenium center electrode tip, copper core construction, and a projected square platinum ground electrode design to support consistent spark delivery across a wide range of late-model and performance applications.

Compatible With Lexus GX550, LS500, LX600, and LX700h; Toyota Sequoia and Tundra; Nissan Z; and select INFINITI and Nissan performance models, this plug is a direct replacement choice for vehicles that call for NGK LKAR8BHX specifications. The NGK Ruthenium HX line focuses on high ignitability and stable operation for modern ignition systems.

Key Features

• Ruthenium center electrode tip for durable spark performance
• Projected square platinum ground electrode design for high ignitability
• Copper core center and ground electrodes for efficient heat transfer
• 5000 ohm resistance for modern ignition system requirements
• Pre-gapped at .032 inches, with application-specific gap notes listed below
• Flat seat, 12 mm thread diameter, 26.5 mm reach, and 14 mm hex size
• NGK part number 91784 / LKAR8BHX

Product Details

NGK has long supplied original equipment spark plugs for domestic and import vehicles, and this Ruthenium HX High Ignitability Spark Plug reflects that OE-focused engineering approach. The copper core construction helps manage heat, while the ruthenium tip supports consistent ignition under demanding driving conditions. For applications such as the 2023-2025 Toyota Sequoia, 2022-2025 Toyota Tundra, 2024-2025 Lexus GX550, and 2023-2025 Nissan Z, this plug is specified to match the vehicle’s ignition requirements and gap settings. This part cross-references Four Seasons (e.g., 91784) for the same application.

What It Helps Address

• Rough idle caused by worn spark plugs
• Hard starting from weak or inconsistent spark output
• Misfire conditions related to plug wear or incorrect gap
• Reduced throttle response from degraded ignition performance
• Maintenance replacement for OE-specified NGK applications

Installation Notes and Tips

• Verify the vehicle’s required gap before installation; listed fitments include .028, .032, and .044 inch specifications depending on application.
• Confirm the correct application by year, make, model, and engine specification before ordering.
• Use the proper torque procedure for the cylinder head material and plug seat type.
• Inspect ignition coils and boots during service to avoid repeat misfire concerns.
• Part number 91784 should be matched to the vehicle’s OE-equivalent spark plug specification.

Quality Assurance

NGK is a major OE spark plug supplier with decades of automotive manufacturing experience and global distribution support. The brand’s OE legacy and focus on original equipment standards make this NGK 91784 spark plug a dependable service part for compatible Lexus, Toyota, Nissan, and INFINITI applications.