One of my functions in temperature testing and anaylsis. If people want to waste a lot of time and effort trying to read engine temps from spark plugs, be my guest. I'll post a 200C plug pic a bit later. However, you cannot know what an engine temperature is by reading plugs alone. A data stream is mandatory. Reading a plug is best left for determining mixture settings. A perfect mixture setting indication on a spark plug is destroyed by elevated running temps.