[Healeys] Coolant Mixture‏

[Leonard Berkowitz]

Anti freeze is not only to prevent freezing.  Any material disolved in water changes both the freezing and the boiling points.  (Lowers the freezing and raises the boiling)  The result is that not only do you protect from freezing you also help prevent boil over.  Since our cars run hot that's a good idea.  By the way raising the pressure also raises the boiling point.  Hence most cars now have significantly higher relief valves (radiator caps) then they used to.