NGK 91725 Spark Plug

NGK Laser Iridium Spark Plug for Mazda MX-5 Miata

The NGK Laser Iridium Spark Plug 91725 is built for precise ignition performance in the 2006-2015 Mazda MX-5 Miata. It combines an iridium center electrode tip with a nickel ground electrode to support consistent spark delivery and stable engine operation.

As part of NGK’s Laser Iridium Spark Plug line, this plug reflects the brand’s OE-focused approach to ignition components for domestic and import vehicles. Part number 91725 is engineered to meet original equipment standards for durability and dependable performance in the Mazda MX-5 Miata application.

Key Features

• Laser Iridium spark plug for ignition service on the Mazda MX-5 Miata
• Iridium center electrode tip material for precise spark characteristics
• Nickel ground electrode with standard configuration
• Pre-gapped at 0.052 in. for the listed application
• 5,000 ohm resistance for ignition system compatibility
• Tapered seat, 14 mm thread diameter, 25.00 mm reach
• Heat range 6 with a non-removable nut terminal
• NGK part number 91725, manufacturer part number LTR6BI-13

Detailed Description

NGK 91725 is a Laser Iridium spark plug specified for the 2006-2015 Mazda MX-5 Miata. The iridium center electrode tip and copper core support efficient ignition performance, while the standard ground electrode design helps maintain reliable spark delivery under normal operating conditions. With a tapered seat and 0.052 in. pre-gap, this plug matches the listed OE-style application requirements for the MX-5 Miata.

NGK’s long OE supply history and broad vehicle coverage make this spark plug a direct-fit service part for drivers maintaining factory-style ignition performance. If you are replacing worn plugs on a Mazda MX-5 Miata, part number 91725 provides the specified dimensions and heat range for the application.

This part cross-references Four Seasons 91725 for the same application.

Common Issues This Part Can Address

• Misfire caused by worn or fouled spark plugs
• Hard starting related to weak ignition output
• Rough idle from inconsistent spark delivery
• Reduced throttle response from degraded plug performance
• Maintenance replacement for scheduled ignition service on the Mazda MX-5 Miata

Installation Notes and Tips

Verify the plug gap, thread size, reach, and seat type before installation. For this application, the listed gap is 0.052 in., with a 14 mm thread diameter and tapered seat. Follow the Mazda MX-5 Miata service procedure for torque and removal/installation sequence, and inspect ignition coils and boots during spark plug service.

Quality Assurance

NGK is a major OE supplier of spark plugs in North America and manufactures ignition components for a wide range of automotive applications. Part number 91725 is produced to support original equipment standards for durability and operational performance in the listed Mazda MX-5 Miata fitment.