{"product_id":"denso-sk20hr11-iridium-platinum-spark-plugs-4-pack-3421-oem-fit-long-life-ignition","title":"Denso SK20HR11 Iridium Platinum Spark Plugs 4-Pack (3421) — OEM Fit, Long-Life Ignition","description":"\u003cp\u003e\u003cstrong\u003eDENSO SK20HR11 (3421) iridium platinum spark plugs — genuine 4-pack designed for reliable ignition and long service life in compatible vehicles.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003eThese are original Denso spark plugs (part number 3421) sold as a 4-piece set. The SK20HR11 construction combines an iridium center electrode with a platinum ground electrode to provide a fine spark gap, improved wear resistance, and consistent firing across a variety of gasoline engines. This listing includes free shipping within the USA and territories, and each order contains four spark plugs—ready to install as a full-set replacement.\u003c\/p\u003e\n\n\u003ch3\u003eWhat makes the SK20HR11 different from standard spark plugs?\u003c\/h3\u003e\n\n\u003cp\u003eThe SK20HR11 uses premium metals and a refined tip geometry that help maintain a stable spark over time. Iridium and platinum electrodes resist erosion better than conventional materials, preserving gap integrity and ignition consistency under normal driving conditions.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eIridium center electrode for a smaller, more focused spark area\u003c\/li\u003e\n  \u003cli\u003ePlatinum ground electrode to slow wear at the firing edge\u003c\/li\u003e\n  \u003cli\u003eManufactured to Denso OEM tolerances for fit and function\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow do these plugs affect starting and throttle response?\u003c\/h3\u003e\n\n\u003cp\u003eUp-to-spec spark plugs can improve combustion stability, which often translates to more reliable cold starts and crisper throttle transitions. While behavior depends on the vehicle and condition of other systems, fresh plugs remove a common source of misfires and uneven idling.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eCleaner spark reduces misfires and rough idle potential\u003c\/li\u003e\n  \u003cli\u003eConsistent ignition can improve throttle smoothness\u003c\/li\u003e\n  \u003cli\u003eFull 4-plug set restores uniform firing across cylinders\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhich vehicles and situations are these Denso plugs intended for?\u003c\/h3\u003e\n\n\u003cp\u003eThe SK20HR11 (3421) is designed to match applications specified by Denso and many OEMs where this engine heat range and thread size are required. They're best used as a like-for-like replacement or when upgrading worn standard plugs to iridium\/platinum construction.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eDirect replacement where Denso 3421\/SK20HR11 is listed\u003c\/li\u003e\n  \u003cli\u003eRecommended when replacing a full set of engine plugs\u003c\/li\u003e\n  \u003cli\u003eAppropriate for everyday driving and highway use when matched to vehicle specs\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat comes in the box and what should I check before fitting?\u003c\/h3\u003e\n\n\u003cp\u003eThis product ships as a sealed pack of four genuine Denso spark plugs labeled with part number 3421. Before installation, verify thread size, reach, and heat range against your vehicle’s service manual or parts guide to ensure compatibility.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eIncludes four Denso SK20HR11 (3421) spark plugs per order\u003c\/li\u003e\n  \u003cli\u003eInspect thread and electrode condition; check OEM gap if needed\u003c\/li\u003e\n  \u003cli\u003eUse correct torque and anti-seize\/coil-specified procedures during installation\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWho is this for: This 4-pack is intended for vehicle owners, independent mechanics, and service shops seeking genuine Denso replacement plugs in the SK20HR11 (3421) specification. Choose this set if your vehicle’s maintenance schedule calls for these part numbers or if you want an OEM-grade iridium\/platinum option for improved durability and consistent ignition. Free shipping within the USA and territories makes it convenient for anyone replacing all four plugs at once.\u003c\/p\u003e\n\n\u003csection class=\"product-faq-snippet\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Are these Denso plugs sold as a full set?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Yes — each order contains four genuine Denso SK20HR11 (3421) spark plugs, packaged for a full-set replacement.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Do these plugs include free shipping in the USA?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Yes — this item ships free to all U.S. states and territories.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"Denso","offers":[{"title":"Default Title","offer_id":48084140654750,"sku":"B00PD6EWPU","price":63.43,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0781\/2041\/9486\/files\/denso-3421-front-packaging_762a4f7c-000d-49f3-ac04-2cc19ceebfae.jpg?v=1785847249","url":"https:\/\/northtrailauto.ca\/products\/denso-sk20hr11-iridium-platinum-spark-plugs-4-pack-3421-oem-fit-long-life-ignition","provider":"North Trail Auto","version":"1.0","type":"link"}