JBW sums up my thoughts on waterless coolants, my fear is that it's use could be masking another issue.
Last year, on my (modest) 13 year old 4/4, I had the original radiator replaced with a Mulfab unit. Results are that the car runs consistently approx. 10C to 15C cooler and the heater is now more effective. I can only assume the latter is as a result of better water flow around the system.
I have owned the car for 11 years, and with hindsight the cooling had become less efficient with time and mileage (now 38,000)

Bud
4/4 "Stanley"