now a cooloer engine performs much better and efficient, some people go a little hotter for winter, if their heater isnt as hot as they would like.

to a point, running a lower temp thermostat will not allow the engine to get warm enough and will kill the heater (cold heat) its a tossup to it runs better or not cooler.... because at cooler temperatures, it is supposed to be able to be advanced more without ping supposedly equalling more power, if so tuned....

i have a thread recently about using a higher pressure radiator cap and a lower temp thermostat.... look into that thread