Denso 3421 Spark Plug

Denso Iridium Long Life Spark Plug 3421

Denso 3421 is an Iridium Long Life spark plug built for OE-style ignition performance, durability, and emissions control. It is a direct-fit option for a wide range of Toyota, Lexus, BMW, Volvo, and other applications where precise spark delivery matters.

The Iridium Long Life line is engineered for extended service intervals and stable ignition performance in demanding daily driving conditions. For shoppers searching for a Denso 3421 spark plug for Toyota Tundra, Lexus GX460, or BMW 328i applications, this plug matches the OE-style design and fitment requirements listed below.

Key Features

• Iridium center electrode tip for consistent spark performance
• Platinum chip ground electrode tip design for durability
• OE-style flat seat construction
• Pre-gapped to 1.1 mm
• 14.00 mm thread diameter with 16.0 mm hex size
• 5000 ohm resistance for ignition system compatibility
• Copper center electrode core and nickel ground electrode core
• Manufactured to OE performance, durability, and emissions standards

Product Details

Denso 3421 is part of the Iridium Long Life product line, which focuses on long-service ignition performance with an iridium firing tip and a platinum-enhanced ground electrode design. That combination supports reliable combustion and steady engine response in vehicles that specify an OE-style iridium plug. This part cross-references DENSO Auto Parts SK20HR11 for the same application.

Compatible With 2017-2023 Lexus GX460, N/A; 2018-2022 Toyota Sequoia, N/A; 2017-2021 Lexus LX570, N/A; 2018-2021 Toyota Land Cruiser, N/A; and 2018-2021 Toyota Tundra, N/A. Additional fitment includes 2005-2017 Toyota Tundra, 2005-2015 Toyota Tacoma, 2003-2013 Toyota 4Runner, 2007-2013 Toyota FJ Cruiser, 2008-2013 BMW X3, and 2004-2010 Volvo V70, among many others listed in the application data.

What This Spark Plug Helps Address

• Rough idle caused by worn ignition components
• Hard starting from weakened spark output
• Misfire-related drivability concerns
• Reduced fuel economy from inconsistent combustion
• Maintenance intervals that call for OE-style iridium replacement

Installation Notes and Tips

Verify engine application, thread reach, seat type, and heat range before installation. Use the listed pre-gap as a reference and confirm the gap against the vehicle service specification if required. Clean the plug wells, inspect ignition coils and boots, and torque the plug to the manufacturer’s specification for the vehicle. Fitment examples include Toyota Tundra, Lexus GX460, and BMW 328i applications, so always match the exact year and engine configuration shown in the fitment data.

Quality Assurance

Denso manufactures this spark plug to OE performance, durability, and emissions standards. The Iridium Long Life design is intended for consistent ignition quality in factory-specified applications such as Toyota Land Cruiser, Lexus LX570, and BMW X5 models listed in the fitment data.