The Denso 5285 is not a standard "copper" plug. It features a .
: The ground electrode features a unique U-shaped groove that allows the flame kernel to expand more quickly. This leads to more complete combustion and reduced carbon fouling. denso 5285
As of April 2026:
If you are holding this spark plug, you are holding a specific piece of engineering designed to solve a problem for modern ignition systems. The Denso 5285 is not a standard "copper" plug