I too am running 50/50 coolant with Water Wetter. All I know is what my readings were on my blaZt before and after I installed a new (used) fan clutch and a new rad.
Last week was my last drive before winter storage and the outside temp was 40F. The 40km roundtrip rural/highway had steady temps of 158F -159F as per my blaZt. All I know is that my plenum no longer gets blazing hot each and every time I drive the the Z.