NGK 373 Spark Plug

NGK Laser Iridium Spark Plug for Subaru Legacy

The NGK 373 is a Laser Iridium High Ignitability spark plug built for precise ignition performance and OE-style serviceability. It is a direct-fit choice for 2010-2012 Subaru Legacy applications that call for a high ignitability plug with a 0.032 in. gap.

Key Features

• Laser Iridium High Ignitability design for consistent spark delivery
• Iridium center electrode tip with copper core for stable ignition performance
• Projected square platinum ground electrode tip design
• Standard ground configuration with one ground electrode
• 5,000 ohm resistance
• Flat seat, 14.00 mm thread diameter, 26.5 mm reach
• 5/8 hex size and non-removable nut terminal
• Manufacturer heat range 6
• Pre-gapped to .032 in.

Product Details

NGK 373, also identified as SILFR6B8, is part of NGK’s Laser Iridium High Ignitability line, a product family focused on OE-level ignition consistency and durability. NGK has long supplied original equipment spark plugs for domestic and import vehicles, and this plug reflects that background with an iridium-tipped center electrode, nickel ground electrode core, and a projected electrode profile that supports reliable spark exposure. This part cross-references Autolite 373 for the same application.

Compatible With 2010-2012 Subaru Legacy, N/A. The fitment notes specify that the OE spark plug is high ignitability and that replacement with a high ignitability plug is recommended for optimal performance. NGK 373 is also referenced for Subaru OE numbers 22041AA760, 22401AA760, and 22401AA761.

Common Issues This Part Helps Address

• Rough idle caused by worn spark plug electrodes
• Hard starting from weakened ignition output
• Misfire conditions related to plug wear or incorrect gap
• Reduced throttle response from inconsistent spark delivery
• Service interval replacement for Subaru Legacy ignition maintenance

Installation Notes and Tips

Verify the engine application and confirm the specified 0.032 in. gap before installation. Use the correct 5/8 in. spark plug socket and follow the vehicle manufacturer’s torque specification to avoid thread or seat damage. Inspect ignition coils and plug wells during service, especially on Subaru Legacy models where access can be tighter than on other layouts.

Quality Assurance

NGK is a major OE spark plug supplier with more than 80 years of automotive manufacturing experience. The brand’s North American and global production and distribution network supports consistent product availability and OE-focused quality control for ignition service.