For every 10 degrees cooler the engine runs it requires 1 less octane point. (I.E. more boost, timing, etc per octane from pump gas)
You wonder why I could run my race program until the mean heat of summer...
Well besides good tuning
Even now I switch to it if I'm driving at night.
What difference is that on a stock or mail order chip car. Not much if any.
For ref
Stock t-stat starts to open at 190-192.
Stock fans are 216/224.
