QQ, just changed the thermostat in my V6. I have been running premixed green coolant since a complete engine rebuild. Everything was clean as a whistle, new radiator core, pump and so on. Noticed a build up of a hard calcium on the thermostat housing, just a few areas around the neck. inside everything seemed OK..
What is everyone using in their engines?
Cheers Mark

I use Cat coolant .
Probably the worlds widest used coolant in truck , mining , and heavy machinery engines that cost millions . 
I also use it in all my machines in my line of business and my personal cars . 
Used ELC for the last 20 years and never once had a problem with corrosion or cooling issues . 
Its bloody good stuff . 
http://www.bmgs.com.tr/doc/GucSistemleri/MusteriDestek/CAT-ELC.pdf
If anyone needs any give me a shout , have several hundred 5 litre tubs which is more than enough for a car  as you dilute with water 

This thread might be of interest:
 
http://www.classic-ford.org/cfp/tm.aspx?m=81745
 
 

Thanks for the info guys.
Mark