NGK Iridium IX Spark Plugs LFR5AIX11 6-Pack — Fine-Wire Iridium, 14mm Thread, Extended Life

These NGK Iridium IX spark plugs (part number LFR5AIX-11, stock 4469) combine a fine iridium center electrode with a tapered nickel-alloy ground tip and ceramic insulator to provide a precision spark source for fuel-injected and turbocharged engines. With a 0.044" (1.1 mm) factory pre-gap, mid-projection center electrode and a resistor built in, they’re designed to improve ignition consistency and resist wear compared with standard plugs. The plugs use a crush washer seat, 5/8" (16 mm) hex, 14 mm thread diameter and a 26.5 mm reach, matching many Nissan, Infiniti, Hyundai, Kia, Toyota and other OEM applications listed by year and engine size.

How do these NGK Iridium plugs affect engine performance?

Iridium’s high melting point allows a much finer center electrode, concentrating the spark and improving combustion efficiency. That concentrated spark often yields smoother idle, quicker throttle response and more consistent firing under load without changing your engine tuning.

• Fine-wire iridium center electrode for focused spark energy
• Taper-cut nickel ground tip to optimize flame propagation
• Precision laser construction for consistent spark gap and timing

What longevity and maintenance benefits do they offer?

Iridium electrodes wear far less than conventional materials, so these plugs maintain their gap and performance longer. NGK rates these plugs as a performance-grade upgrade with an expected extended service life compared to standard copper plugs, reducing replacement frequency when used in recommended applications.

• Durable iridium tip resists erosion for stable gap over time
• Crush washer ensures correct sealing at installation
• Resistor type reduces radio frequency interference for electronics

Which vehicles and engine types are compatible with LFR5AIX-11?

These plugs fit many 3.5L and 4.0L V6 engines and select 2.7L and 3.8L applications from manufacturers including Nissan, Infiniti, Hyundai, Kia, Toyota and Suzuki. Always cross-check part numbers and build dates against your vehicle’s specifications before ordering to confirm correct reach, thread size and heat range.

• Common fits: Nissan 350Z, Altima, Maxima, Murano, Frontier, Pathfinder, Xterra
• Infiniti models: FX35, G35, I35, M35, QX4 for listed years
• Hyundai/Kia/Toyota compatible engines specified by year and build date

Are these plugs easy to install and what are the technical specs to verify?

Installation follows standard spark-plug procedures: torque to manufacturer spec and use the crush washer to seal. Verify thread diameter, reach and hex size to ensure the plug seats properly and doesn’t contact combustion chamber components.

• Thread: 14.0 mm (0.551") with 26.5 mm (1.043") reach
• Hex: 5/8" (16 mm); insulator height 50.5 mm (1.99")
• Pre-gap: 0.044" (1.1 mm); manufacturer heat range 5

Who this is for: Drivers and technicians seeking a direct-fit, performance-oriented replacement spark plug for compatible 6-cylinder engines will value the NGK 4469 Iridium IX. It’s suited to enthusiasts, fleet vehicles and everyday drivers who want a long-lasting, OEM-style upgrade that improves ignition consistency and minimizes maintenance frequency. Verify fitment against your vehicle’s year, engine and build-date details before purchase.