Fake NGK Spark Plugs

[Stichill_imp]

Gin60: I am not understanding - why does the top plug look spent? Are you just comparing thread pitch and ceramic electrode insulation length? Everything else is hard to compare.

Even the ceramic insulation is tricky to compare in the photo image because the lower image is slightly twisted toward the viewer.

The center electrode is clearly not the correct alloy, e.g. platinum, iridium. etc. It was just some ordinary metal (copper, brass, steel) machined to look like a fine-tipped, high-performance alloy, so it burned away and opened the spark gap.

This larger gap would greatly stress the ignition coil(s).