ORIGINAL: combatpigg
If the element is consumed to a chalky grey/white, the plug died with honor. If the element is missing and all there is left is a smoking hole, then that is your indicator that something is wrong.
Didn't someone, somewhere publish a chart, or picture, or text, or something about plug failures, what they look like and what they could be attributed to? (You know, kinda like the old spark plug tuning charts.) I feel like I remember seeing something like that in my Internet travels, or am I hallucinating.
-Joe