My pros are:
- system runs at 7 psi or less; less likely to have leaks
- hotspots if true
- warms up quicker in the morning
- no Mr. Coffee sounds from the turbo after engine shutdown, FWIW
- cost, and catching it to re-use it when draining, because of cost
- higher average temperature
- can't top up with water in an emergency
In general, these new coolants work, but have a lower thermal transfer coefficient than water/glycol (water alone has the highest)
NPG+C is less 'efficient' than water at transporting heat, however the effective difference in a real world application is minimal. Using temperature probes at various points on the engine, the thermostat housing read 165* with water, and 175* with NPG+C after a highway jaunt. That is in F*. Also keep in mind, that this difference is comparing 50/50 mix with a single core radiator, and fully stock setup, to NPG+C with a dual-core race radiator, upper shroud, and liscense plate relocation. I would've liked to get a reading of the temperature gauge sending location, but couldn't fit the probe back there between the firewall, as my hands are too large.
Other things to note, with the AC on, the temperature rises to about 3/4ths of the way to hot, to 5/6ths of the way to hot, depending on how hard you are pushing the car. The temperature drops steadily (not quickly) down to a 'normal' operating temperature once you return to cruising at ~ 50 mph. At highway speed (80 mph where I am) the temp stays steady at about 3/4's to the H.
This caused an issue with the AC system, and a spike in temperature accordingly, because the added underhood temperature increased the pressure of the AC system by about 12-15 pounds. The solution seems to be to run less coolant in the AC system to compensate; and so far has prooven to work; and still cool adequately at about 39*F at the vent