Just some documentation on an old thread. Here's a pic of my grey head 582 plugs after 31 hours. I think they're looking pretty healthy.
Fuel: Premium unleaded 91 AKI no Ethanol
Oil Injection: Amsoil full synthetic either Interceptor or HP Marine
Mixture with HacMan system set EGT to 1150 F in cruise.
No idea why some plugs are Cad plated and some are not. They're all out of the same box/ order.