As the beta tester for the Evans NPG+ lifetime coolant, I was struck with a dilemma today. Jinking around through traffic and stop lights the high temp. idiot light came on. Not a problem with the evans since it boils at 375F but, at what temps do other engine problems develop? How do I know when the engine is too hot to run when I'm already off the scale?? Seems like 300+ degrees would at least fry the plastic cooling fan if not something more important. While this is not an issue on my highway comute to work, it will certainly be on hot summer days in traffic because today wasn't even a hot day by florida standards. What do you guys think is the upper limit in terms of running temperatures?? And I'm open to suggestions on how to monitor these higher temps.