Mercury - ACDelco Double Platinum Spark Plug Ignition System Nickel Alloy & Copper Core 8M0129146. Overview. There's a particular kind of comfort that comes from an engine that fires immediately-no hesitation, no uneven rumble, just a clean, confident start that tells you the day's going to go right. That feeling isn't accidental. It comes from parts like the Mercury 8M0129146 ACDelco GM Original Equipment Double Platinum Spark Plug doing their job exactly as they should. When you're pushing a h