You can also add water wetter to a 50/50 coolant to improve the heat transfer. In actual practice, I have ran distilled water with water wetter in my race bike for 12 years (change it every year). The radiator and rest of the cooling system components are pristine. Of course, this setup offers no freezing protection.Use a premix antifreeze/coolant and put your worries aside.
Water wetters work to help transfer heat better. My company make a water wetter called Motor Max.
EPA testing shows exactly what it does to cylinder walls and combustion by enhancing the ability of the coolant to absorb heat from the motor and dissipate it more efficiently.
Don't confuse this with the running temperature of the motor, it will always be what the thermostat is set for.
However, cylinder walls are cooled quicker and more evenly which the reports prove reduces emissions considerably and yields a slight mpg increase.