Well, I looked it up in my owner's book (what VW says about coolant concentrations).  So, here it is, from page 104 in the owner's book for my Volkswagen Vanagon GL Campmobile (and I don't know anyone who calls these vehicles "Campmobiles", but plenty of people call them "campers"):

"The coolant consist of a mixtur of water and the manufacturer's coolant additive G 11 -- antifreeze on glycol basis with anticorrosion additives (40% for USA models; 50% for Canadian models)."

Then, a little further down:

"The coolant additive proportion must be at least 40% but not more than 60% to maintain the antifreeze protection and the cooling efficiency."

Still another place:  "For year round driving, antifreeze is added at the factory for temperatures down to:  -13 F/-25 C  (USA);  -40 F/ -40 C (Canada) ."

So, I knew the recommendation was for a higher concentration for Canada, but I had it too high for both Canada and the U.S., so far as the owner's book is concerned.  For my money, -13 F isn't adequate for parts of the U.S., even Oklahoma, as we had temperatures below that in parts of the state this week (and we do most years on one or two occasions, usually out west in the Panhandle).  Coldest here was -7 F Thursday morning.  It is 41 F right now, and the 15 inches of snow is melting.  We expect more tonight and Tuesday, however.

Since I see reports most winters for temperatures below -35 F in parts of the upper plains states and the northern Rockies, and for Alaska and parts of Canada, if I drove in those places in winter, I'd provide the 60% concentration mentioned elsewhere.

mcneely