I will run a 180 in the summer but switch to a 200 in winter so the heater works better. I like warm feet!
On edit; what kind of a rig are you running, and what are you using it for? My advise is for the 66 that I have. Now if your in a rig that has marginal cooling or poor air flow then my advise may be different. I once had cooling problems in a V-8 Corvair and found that going to a 210 degree thermostat cured most of the problems. The GM engineer that helped me with the problem explained that with the higher heat that the BTU's would transfer to the cooling air more redilly than with a lesser difference in temp between the cooling air and radiator. So sometimes a cooling problem can be cured with a hotter thermostat. The engine doesn't much care as long as the cooling fluid stays fluid and will carry the excess heat from the engine. Please read that last line again before flaming.
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