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

NGK 4469 Iridium IX LFR5AIX11 spark plugs are high-performance, fine-wire iridium plugs designed to deliver more reliable ignition, improved throttle response, and long service life for compatible 6-cylinder engines.

These NGK Iridium IX plugs (Part No. LFR5AIX-11, Stock 4469) combine a durable iridium center tip with a taper-cut nickel ground electrode and a ceramic insulator to produce consistent sparks under demanding conditions. Built with a 0.044" pre-gap (1.1 mm), 14.0 mm thread diameter, and a 26.5 mm reach, they suit a range of Hyundai, Infiniti, Kia, Nissan, Suzuki, and Toyota applications where precision ignition and longevity matter. The plugs include a crush washer and a non-removable nut electrical terminal for straightforward installation and secure connection.

How do these NGK Iridium IX plugs improve everyday driving?

Iridium’s fine-wire center electrode requires lower voltage to produce a focused spark, which helps the air/fuel mixture ignite more completely. Drivers commonly notice steadier idle, crisper throttle response, and smoother acceleration after swapping to these plugs.

• Fine-wire iridium center electrode for concentrated spark energy
• Precision laser-welded construction for uniform ignition
• 0.044" pre-gap tuned for listed compatible engines
• Resistor design reduces radio frequency interference

What makes the LFR5AIX11 different from standard plugs?

Unlike conventional copper or platinum plugs, these NGK Iridium IX units use a hard iridium tip on a copper core, blending heat transfer with a wear-resistant electrode. The taper-cut ground electrode and J-gap layout optimize flame travel and combustion efficiency without changing factory ignition components.

• Iridium tip on copper core balances durability and conductivity
• Taper-cut ground electrode improves flame propagation
• Mid projection center electrode preserves combustion chamber geometry
• Flat seat and 5/8" (16 mm) hex for common socket sizes

Are these plugs easy to install and maintain?

Installation is straightforward for anyone with basic mechanical tools: they use a standard 14.0 mm thread and include a crush washer for seat sealing. They are engineered for long intervals between changes, helping reduce routine maintenance when matched to the recommended service schedule.

• Reach: 1.043" (26.5 mm) — confirm compatibility before fitting
• Crush washer included for proper sealing on flat-seat engines
• Hex size 5/8" (16 mm) fits common spark plug sockets
• Resistor type helps protect vehicle electronics and reduces interference

Which vehicles are these NGK LFR5AIX11 plugs compatible with?

NGK provides a broad compatibility list for many 6-cylinder engines across several manufacturers; check build dates and engine displacement before ordering. They match many Hyundai, Infiniti, Kia, Nissan, Suzuki, and Toyota models that require a 14 mm thread, 26.5 mm reach, and a 0.044" gap.

• Hyundai Genesis (2009 3.8L before 5/1/2008) and Santa Fe (2007–2009 2.7L)
• Infiniti FX35, G35, I35, M35 and QX4 3.5L 6-cylinder years listed
• Nissan 350Z, Altima, Maxima, Murano, Frontier, Pathfinder, NV series, Quest, Xterra
• Toyota 4Runner, FJ Cruiser, Tundra models from 6/2013 onward; Kia and Suzuki models listed

Who is this for: drivers, technicians, and performance-minded owners seeking a durable, high-energy spark plug that fits many naturally aspirated and turbocharged 6-cylinder engines. If you want reduced misfire risk, more consistent starts, and extended plug life compared with standard copper plugs, the NGK 4469 Iridium IX LFR5AIX11 six-pack is built for those upgrades. Always verify engine compatibility, thread size, and reach against your vehicle’s service manual before installation.