Ford Motorcraft Double Platinum Spark Plugs for 4.6L, 5.4L, 6.8L Applications (Sets of 8, 10) SP-509X SP-509-X HJFS-24FP

**Motorcraft SP-509 (HJFS-24FP) Double Platinum Spark Plug** is a genuine OEM ignition component engineered by Ford Motor Company for reliable performance in select Ford, Lincoln, and Mercury vehicles.

This high-quality spark plug features **double platinum** electrode tips (platinum on both the center and ground electrodes), providing excellent resistance to oxidation, arc erosion, and fouling while delivering consistent spark for smooth engine operation. The nickel-plated shell enhances corrosion resistance and improves overall appearance and longevity. Its multi-rib insulator design helps prevent misfires by effectively blocking flashover, even under demanding conditions.

Key specifications include:
– **Thread size** — 12 mm
– **Reach** — typically compatible with specific engine designs (often around stock heat range equivalent to many applications)
– **Hex size** — 9/16 inch (14 mm) for standard installation tools
– **Resistor type** — Yes (built-in resistor to suppress electromagnetic interference)
– **Heat range** — Matched to Ford’s factory calibration for optimal performance
– **Direct ignition compatibility** — Designed for use with brown ignition coil boots in many applications

The SP-509 is specifically recommended as the factory-replacement spark plug for various modular V8 engines, including:
– 4.6L 3V (e.g., 2008–2010 Ford Mustang GT)
– 5.4L 3V (e.g., select F-150, Expedition, Explorer, and Lincoln models from late 2007 onward)
– 6.8L V10 (e.g., Super Duty trucks and certain commercial applications up to around 2019)

Tested to meet or exceed Ford’s strict performance, emissions, and durability standards, it helps eliminate misfires, improve fuel efficiency, reduce emissions, and support extended service intervals compared to standard plugs. Often superseded or listed as SP-509-X in newer packaging, it remains a direct-fit, high-reliability choice for maintaining original engine performance and warranty compliance in compatible vehicles.