{"product_id":"denso-iridium-long-life-spark-plugs-set-8pc-3421-with-0-043-pre-set-gap-extended-life","title":"Denso Iridium Long Life Spark Plugs Set — 8pc (3421) with 0.043\" Pre-set Gap, Extended Life","description":"\u003cp\u003e\u003cstrong\u003eThese are genuine Denso Iridium Long Life spark plugs — an 8-piece set (model 3421) with a 0.043\" (1.1 mm) pre-set gap and iridium-tipped electrodes for reliable ignition and extended service life.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003eIf you need a complete replacement set for routine maintenance or a tune-up, this pack supplies eight factory-original Denso 3421 spark plugs. Each plug features an iridium core electrode designed to resist wear and maintain a stable spark over many miles. The set ships in original Denso packaging and includes the hardware required for straightforward installation; verify vehicle fitment using your dealer fit tool or Amazon’s Confirmed Fit before ordering.\u003c\/p\u003e\n\n\u003ch3\u003eHow do Denso Iridium plugs improve ignition consistency?\u003c\/h3\u003e\n\u003cp\u003eIridium-tipped electrodes use a harder, higher-melting-point metal than conventional plugs, which preserves the electrode shape and gap. That stability helps maintain a consistent spark pattern and can translate to smoother engine starts and steady combustion over time.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eIridium core for reduced electrode erosion\u003c\/li\u003e\n  \u003cli\u003eStable 0.043\" (1.1 mm) gap out of the box\u003c\/li\u003e\n  \u003cli\u003ePrecise manufacturing for uniform spark delivery\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eAre these plugs a direct fit for my vehicle?\u003c\/h3\u003e\n\u003cp\u003eModel 3421 is an OEM-style plug intended as a direct replacement for applications that specify Denso 3421. Compatibility depends on your engine’s required thread size, reach, and heat range, so always confirm fitment before purchase.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eSold as an 8-piece genuine Denso set for multi-cylinder engines\u003c\/li\u003e\n  \u003cli\u003eCheck thread length and hex size against your vehicle specs\u003c\/li\u003e\n  \u003cli\u003eUse online fitment tools or consult a parts dealer for verification\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat should I expect during installation and routine maintenance?\u003c\/h3\u003e\n\u003cp\u003eInstallation is the same as other threaded spark plugs: remove old plugs, inspect the threads and boots, and torque new plugs to the manufacturer’s specification. Because the gap is factory-set to 0.043\" (1.1 mm), you typically won’t need to re-gap, though a quick check is recommended during service.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eFactory gap reduces initial setup time\u003c\/li\u003e\n  \u003cli\u003eFollow vehicle torque specs to avoid thread damage\u003c\/li\u003e\n  \u003cli\u003eInspect ignition boots and wires or coils while replacing\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow long can I expect these plugs to last compared with standard plugs?\u003c\/h3\u003e\n\u003cp\u003eIridium electrodes are engineered for extended wear resistance, which commonly yields longer service intervals than conventional nickel plugs. Actual life varies by driving conditions, engine tune, and maintenance habits.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eIridium construction for prolonged electrode life\u003c\/li\u003e\n  \u003cli\u003eConsistent performance under typical driving loads\u003c\/li\u003e\n  \u003cli\u003eMonitor for misfires, rough idle, or increased fuel use as replacement triggers\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWho is this for: This 8-piece Denso 3421 Iridium Long Life spark plug set is geared toward DIYers, independent mechanics, and fleet technicians who need a full-kit replacement for eight-cylinder or multi-plug applications. It’s ideal when you want OEM-quality parts in original Denso packaging, a pre-set 0.043\" (1.1 mm) gap to save setup time, and the longer-wearing characteristics of iridium electrodes. Confirm your vehicle’s required plug specification before purchasing to ensure correct fit and safe installation.\u003c\/p\u003e\n\u003csection class=\"product-faq-snippet\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: What gap size do these Denso 3421 plugs have?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: They come pre-gapped to 0.043\" (1.1 mm) from the factory.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Is this an OEM-quality replacement pack?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Yes — the set contains genuine Denso parts in original packaging for direct replacement use.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"Denso","offers":[{"title":"Default Title","offer_id":55161252348247,"sku":"B0721V9JYZ","price":96.26,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1050\/1524\/7191\/files\/denso-front-packaging.jpg?v=1790323270","url":"https:\/\/britishgarage.co.uk\/products\/denso-iridium-long-life-spark-plugs-set-8pc-3421-with-0-043-pre-set-gap-extended-life","provider":"British Garage","version":"1.0","type":"link"}