NGK Iridium Spark Plugs LTR5IX-11 6-Pack — Direct-Fit 6-Cylinder, Fine-Wire Iridium

NGK LTR5IX-11 (Stock #4344) iridium spark plugs—six high-performance plugs engineered to restore reliable ignition and consistent combustion in compatible 6-cylinder engines.

These NGK LTR5IX-11 iridium spark plugs are a direct-fit replacement for a wide range of domestic and import 6-cylinder vehicles, offering a durable iridium center electrode, integrated resistor, and factory-specified reach and hex size. Each plug in this 6-pack features a fine-wire iridium core with a tapered seat, mid-projection insulator tip, and a pre-set gap matched to popular engine applications. The result is improved ignition consistency, reduced misfires, and a stable spark gap over service life when installed to the manufacturer’s specifications.

Which vehicles and engine sizes are these NGK 4344 plugs compatible with?

This set fits numerous GM, Ford, Mazda, Lincoln, Isuzu and related platforms that use NGK LTR5IX-11. Compatibility covers various model years and 3.5L–4.3L 6-cylinder engines; gap and pre-gap values depend on the specific vehicle.

• GM family: Buick Rainier, Chevrolet Express/Silverado/Trailblazer, GMC Envoy/Sierra/Savana (2002–2024 ranges listed)
• Ford & Lincoln: Edge, Flex, Fusion, Taurus, MKX/MKZ/MKS/MKT (2007–2012 ranges)
• Mazda & others: Mazda 6, CX-9, Mercury Sable, Oldsmobile Bravada, Isuzu Ascender (2002–2015 ranges)
• Verify exact year/engine combo and recommended gap: examples range from 0.040" to 0.052" factory gaps

What are the key technical specs and why do they matter?

These plugs use a fine iridium center electrode with a nickel ground electrode in a J-gap layout, plus a 5000-ohm resistor. Their materials and geometry are chosen to keep ignition sharp, limit gap growth, and reduce electrical noise.

• Material grade: Iridium center; copper core for thermal stability
• Thread: 14.0 mm diameter with 25.0 mm reach and tapered seat
• Hex/insulator: 5/8" (16 mm) hex; 2.07" (52.5 mm) insulator height
• Electrical: 5000-ohm resistor; non-removable terminal

How do these NGK iridium plugs impact performance and maintenance?

Iridium’s high melting point and fine-wire design produce a focused, consistent spark that helps combustion stability and fewer misfires across service intervals. Their construction also resists corrosion and limits electrode wear, which maintains ignitability longer than standard plugs.

• Sharper spark focus for improved combustion initiation
• Reduced gap erosion and longer service life compared with conventional plugs
• Diminished radio-frequency interference due to built-in resistor
• Corrosion-resistant shell for durable thread engagement and removal

What installation details should I check before fitting these plugs?

Confirm thread pitch, reach, and seat type match your engine to avoid damage. Use the vehicle manufacturer’s torque and gap specifications; do not re-gap beyond recommended tolerances for iridium plugs.

• Pre-gap shown: typically 0.044" (1.1 mm) or vehicle-specific values (0.040"–0.052")
• Reach: 25.0 mm (0.984") — verify this suits your cylinder head
• Torque to OEM spec and use anti-seize only if manufacturer allows
• Replace ignition coil boots or wires if worn when servicing plugs

Who is this for: automotive DIYers, independent repair shops, and fleet managers looking for a direct-fit, factory-grade iridium spark plug solution for 6-cylinder GM, Ford, Mazda, Lincoln and related vehicles. Choose this 6-pack NGK LTR5IX-11 set when you need long-lasting ignitability, reduced misfires, and an OEM-compatible replacement meeting original heat range and reach specifications.