Went on a 800+ mile trip this past weekend and got stuck in alot of stop and go traffic. My powervision showed engine temp got up to 381 deg a few times. So how hot before getting worried? It ran fine, never cut off and I'm running syn3 right now but didn't notice any defference in engine temps after the change.

 

Assuming that's from the temp. sensor on the cylinder, 381 is fine. The cylinders can really get up near 500* on a super hot day in traffic.