I used to buy a gallon of Evaporust from Amazon for about $16 with free shipping, but it's nearly double that now.

Haven't priced it at my FLAPS or Walmart, as my need for it is much less and I still have some left for small parts. It would take a few gallons to fill the cooling system.
Wow, I have a little background in chemistry, but that link went WAY over my head.

All I know is that Evaporust works.