NGK 91657 Spark Plug

NGK Laser Iridium Spark Plug 91657

NGK 91657 is a Laser Iridium High Ignitability spark plug built for OE-style service in modern Toyota and Lexus engines. It combines an iridium center electrode, platinum ground tip, and a high-ignitability multi-ground design to support consistent spark performance, reliable starts, and long service life.

Key Features

• Laser Iridium High Ignitability design for OE applications
• Iridium center electrode tip for durability and stable ignition performance
• Platinum ground electrode tip for even wear in distributorless ignition systems
• Fine-wire center electrode and hybrid dual fine electrode ground design
• Copper core and high-grade ceramic insulator to help control heat
• Resistor spark plug with 5,000 ohm resistance
• Pre-gapped to 0.032 in. / 0.8 mm
• M14 x 1.25 thread, 5/8 in. hex, flat seat, 1.043 in. reach

Product Details

NGK’s Laser Iridium High Ignitability line is engineered for original equipment service requirements, with materials selected for durability and dependable ignition under daily driving conditions. The iridium center electrode is paired with a platinum ground electrode tip and a multi-ground configuration to promote consistent spark delivery and controlled wear. The copper core and ceramic insulator help manage heat, while the resistor design supports ignition system stability. This part number is also identified as DILFR6N-T and is a direct service-style replacement for select Lexus ES350, IS300, IS350, RX350, RX450h, and Toyota Camry and Tacoma applications.

This part cross-references Anchor 3491 and Four Seasons 91657 for the same application.

Common Problems This Part Can Address

• Hard starting caused by worn spark plug electrodes
• Rough idle from inconsistent ignition output
• Misfire conditions related to aged plugs
• Reduced throttle response from degraded spark performance
• Service interval replacement on OE-recommended ignition systems

Installation Notes

Verify thread size, reach, seat type, and heat range before installation. The plug is pre-gapped at 0.032 in. / 0.8 mm, but gap should still be checked against the vehicle service specification before use. Use proper spark plug removal and installation procedures to avoid thread damage in aluminum cylinder heads. Confirm vehicle-specific fitment for Lexus ES350, IS300, IS350, RX350, RX450h, and Toyota Camry or Tacoma applications before ordering.

Quality Assurance

NGK manufactures this Laser Iridium High Ignitability spark plug to OE application standards and tests it to strict quality and durability requirements. The iridium and platinum electrode materials are selected to support long service life and consistent ignition performance in distributorless ignition systems.