Land Rover/Jaguar 4.2L 4.4L Iridium Platinum Spark Plug IFR5N10 7866, Engine burns more efficiently

Land Rover Range Rover, Range Rover Sport, and Jaguar XJ/XK (4.2L and 4.4L) use iridium platinum spark plug IFR5N10 (OEM 7866). Placed in spark plug hole, ignites mixture for efficient combustion and smoother power. Installation difficulty: medium; 1-1.5 hours; torque to spec with a torque wrench. If idle jitter, weak acceleration, increased fuel consumption, or check engine light, electrode wear or heavy carbon buildup indicates replacement.