NGK Spark Plug Stock # 3521

The NGK Spark Plug Stock # 3521 is a premium iridium spark plug engineered for reliable ignition performance across a wide range of gasoline engines. This resistor-type spark plug is designed for vehicle owners and technicians who demand consistent cold-start capability and extended service intervals. NGK's iridium construction represents a proven upgrade path for anyone replacing original equipment spark plugs or seeking improved combustion efficiency and fuel economy.

The NGK CR9EIX features a 10 mm thread size with a 0.749 inch reach, allowing direct compatibility with factory mounting applications. The gasket seat design ensures a proper seal against the cylinder head, preventing exhaust gas leakage and maintaining combustion chamber integrity. Iridium electrodes deliver a more focused spark kernel compared to copper alternatives, resulting in faster flame kernel growth and improved ignition efficiency across varying load and rpm conditions. The integrated resistor suppresses electromagnetic interference, protecting vehicle electronics and radio systems while enhancing overall engine performance.

This spark plug suits both routine maintenance and performance-oriented applications where reliable ignition is non-negotiable. Mechanics and DIY technicians rely on NGK's rigorous quality standards for consistent results across domestic and import engines. Installation is straightforward—verify the 10 mm thread pitch and 0.749 inch reach match your engine's spark plug well before installation. The durable construction supports 30,000+ mile service intervals, making the NGK Spark Plug Stock # 3521 a cost-effective choice for long-term engine reliability and responsiveness.