NGK Spark Plug Stock # 3521

The NGK Spark Plug Stock # 3521 is a premium iridium-core spark plug designed for modern gasoline engines that require reliable ignition. This spark plug is ideal for daily drivers, tuned performance builds, and stock restorations, ensuring dependable combustion initiation that mechanics expect from NGK's precision manufacturing heritage.

Constructed with iridium, the CR9EIX spark plug offers a significantly extended service life compared to traditional copper or platinum designs, typically lasting between 30,000 and 50,000 miles. Its design resists erosion and maintains a sharp electrode edge, providing consistent spark voltage across wider gap tolerances. The CR9EIX is engineered for mid-range displacement engines operating at moderate to high RPM, minimizing the risk of detonation and fouling.

Technicians and automotive enthusiasts trust NGK CR9EIX plugs for their compatibility with Japanese, American, and European four-cylinder engines produced over decades. Installation is straightforward, requiring only a 5/8" socket and attention to proper gap and torque specifications. This spark plug is a reliable choice for those seeking both OEM replacements and performance enhancements in their vehicles.