On my 6.0 I took a thermostat and cut the plunger thing out of it, just leaving the plate with the hole in it, It slows down the water in the block to allow it to pick up the heat but does not let it run too fast.
Thermostat is not really necessary on a buggy.
It turns out that plain old distilled water has the highest specific heat of all liquids commonly used for coolant. Water has a specific heat of 1 - meaning one pound of water can absorb 1 BTU for a temperature increase of 1° F.
A 50/50 Ethylene Glycol / water mix has a specific heat of 0.5, meaning it takes only 0.5 BTUs to raise the temperature of 1 pound Ethylene Glycol / water mix 1° F.
A 50/50 Propylene Glycol / water mix has a specific heat of only 0.3.
Therefore, it takes twice as much heat to raise a pound of water 1° F than a 50/50 Ethylene Glycol mix; and over three times as much heat to raise a pound of water 1° F than a 50/50 Propylene Glycol mix.
Ultimately, what this means is that straight water can carry away 50% more heat than 50/50 Ethylene Glycol mix and 70% more heat than 50/50 Propylene Glycol mix per degree per unit volume.
