It sure can't be for a gas engine, and the HFE cannot handle those temps. Do that and you'll be saying C-ya to whatever the engine is in.

They've definately changed their numbers from what they used to publish. A previous high for a gas engine was around 120C. Since the cyulinders "pinked" close to that value it likely helped void some warranty claims. I'll strongly advise people not to run at and above 200C. Even allowing for differences in thermocouple reporting temps induced by deviations in location, 200 is HOT. Ther grey/grey spark plug color consistently occurs near and above 200C. Higher temps even change the color of the outer spark plug base. I burn up 3w's on a regular basis and all of it is done at lower temps than they are referencing. HFE can run hotter than gas but not that hot.