After water damage to my craft after the winter I've been doing some research on antifreeze protection as it pertains to it's concentration. It's been interesting. Check out this link (can I do that?). VERY INFORMATIVE and not what I expected to find...
http://www2.gi.alaska.edu/ScienceForum/ASF6/680.html
http://www2.gi.alaska.edu/ScienceForum/ASF6/680.html