NGK 5688 Spark Plug

NGK Iridium IX Spark Plug 5688 Overview

NGK Iridium IX Spark Plug 5688 is built for drivers who need precise ignition performance and OE-style reliability. This spark plug uses an iridium center electrode, a nickel ground electrode, and a 0.032 pre-gap size for direct-service applications across select Saab, Toyota, and Geo models.

The Iridium IX line focuses on stable spark delivery and durable electrode construction. For shoppers searching for an NGK spark plug for 1988-1994 Toyota Corolla, 1988-1993 Toyota Celica, or 1991-1994 Saab 900 applications, part number 5688 is a direct-reference option to verify against your engine requirements.

Key Features

• Iridium center electrode tip material for consistent ignition performance
• Copper center electrode core material for efficient heat transfer
• Nickel ground electrode core material with standard ground configuration
• Taper-cut ground electrode tip design for focused spark exposure
• 0.032 pre-gap size for listed Toyota and Geo applications
• 14 mm thread diameter, 0.75 reach, and flat seat design
• 5 k? resistance and non-removable nut terminal type
• NGK part number 5688, manufacturer part number BCPR5EIX

Product Details

NGK 5688 is an Iridium IX spark plug engineered around a fine iridium firing tip and a copper-core center electrode to support dependable ignition characteristics. The 5 heat range, 5/8 hex size, and flat seat configuration align with the listed OE-style service applications. This part is commonly searched as an NGK Iridium IX spark plug for Toyota Corolla, Toyota Celica, Geo Prizm, and Saab 900 tune-up service, and the part number 5688 helps confirm the correct reference during replacement.

This part cross-references Monroe Shocks & Struts (e.g., 5688) for the same application.

Vehicle Fitment

• Fits 1991-1994 Saab 900, N/A. Set spark plug gap to 0.028 inches.; Iridium IX Spark Plug
• Fits 1988-1993 Toyota Celica, N/A. Adjust spark plug gap to 0.032 inches.; Iridium IX Spark Plug
• Fits 1990-1992 Geo Prizm, N/A. Adjust spark plug gap to 0.032 inches.; Iridium IX Spark Plug
• Fits 1988-1992 Toyota Corolla, N/A. Adjust spark plug gap to 0.032 inches.; Iridium IX Spark Plug
• Fits 1988 Toyota 4Runner, N/A. Adjust spark plug gap to 0.032 inches.; Iridium IX Spark Plug

Common Replacement Reasons

• Engine misfire or rough idle from worn spark plug electrodes
• Hard starting caused by weak or inconsistent spark output
• Reduced throttle response from degraded ignition performance
• Maintenance replacement for scheduled tune-up service
• Restoration of proper ignition on listed Toyota, Geo, and Saab applications

Installation Notes

Verify engine application before installation and confirm the specified gap for your vehicle. The listed fitments require gap adjustment guidance, including 0.028 inches for the Saab 900 and 0.032 inches for the Toyota and Geo applications shown. Use the correct 5/8-inch spark plug socket and follow the vehicle manufacturer’s torque specification during installation.

Quality Assurance

NGK is a long-established OE supplier and spark plug manufacturer with broad coverage across domestic and import applications. Part number 5688 reflects NGK’s Iridium IX product line and OE-focused manufacturing standards for service replacement use.