I use a Proline product and distilled water for the hot summer, and a modified anti-freeze and water wetter mix for the winter. I have no need for protection below 20F. I mix accordingly.
I can't tell you what the actual engine water temperature differences are. I can say the oil temperature runs at leat 10 dregrees cooler. And possibly as much as 15 degrees cooler in the hottest days. I have had analog oil dip stick readings of 205 before Pww and never higher than 190 afterwards. This past summer I haven't seen higher than 185. This suggests to me that my Amsoil isn't stressing at all.
BTW, the cooling fan comes on at 180.
And for those looking for a bit of excitement: I also use a Scotts permanent filter. It's ribbed for greater cooling as well.