Gotta get more than a gallon. 12 quart capacity.
Well the recommendation is 50/50, he lives in Michigan, and it's a thread started by him about his car. Lol. 50/50.=)
And wow, my tester must be accurate. I mentioned it said 4 quarts in a 12 quart system would be good til 0°F, the chart shows exactly that. Cool, I guess I'll keep it around lolback of the gallon of antifreeze also has a chart on it telling your what mix ratio give you what temp that you can be safe at.
http://www.magers.org/handy/antifreeze.html