If you live in, say Northwest Territories you would mix a bit different than
if you lived in San Diego.  I always said that coolant containers should
allow space for you to add water, with graduated markings in the side, and
the respective temperature zones listed next to them.  There are 50/50
blends available, but remember to be sure it is phosphate free.  It is
better to use, so I have learned, a product ladled "phosphate free" and mix
it with distilled water.