Clean radiator, cool engine, coolant PH, flow, fans, shrouds.

I just looked up some ph for radiator suggestions and this one seems to jive better for what I know about boiler corrosion.
http://www.eutechinst.com/techtips/tech-tips10.htm
So you do not want acidic you want basic. Even normal rain water is acidic at 5.7. I learned that my well water is actually basic at about 8 but that my "softener" is actually just changing the calcium and magnesium ions by replacing them with sodium ions. That actually doesn't sound good to me.
I think bohica2xo is right that the premix is the way to go, they take all these varibles out of the equation.