Be vvvveeerrrrryyyy careful with that Cat permanent stuff (or the same deal from any other company - Cat's isn't anything special really, there are several "permanent" brands out there.)
It has two problems and one serious annoyance:
1. The additives deplete just like any other AF. You need to watch the inhibitor levels just like you do for any other product, AND you need to use the SPECIFIC test kit for that product. None other will work as the chemistry is totally different from the "traditional" nitrite-based stuff (it typically uses organic acids as its inhibitor, which is kinda wierd.)
2. For reasons not real well understood it tends to cause leaks where there weren't any before. Many people have had to go to all constant-torque clamps to keep it from leaking on their engines (these have springs on the winding portion, and maintain tension at all times.) If you start to see evidence of it leaking beware because this problem once it starts will require you to change ALL the clamps on ALL the hoses.
3. The annoyance - it is TOTALLY incompatable with traditional antifreeze. Period. You must make VERY sure to get ALL the old stuff out before you change to it, because when they mix they make a brown sludge that will plug up things you don't want plugged up - like water passages in the engine. Also, if some idiot ever puts traditional stuff in as a top-off, you're screwed. TAG THAT FILL CAP! Distilled water is ok for top-off of course but impacts the freeze point just like it does with traditional stuff.
-20F is a PITA, but you do what you gotta do. Were I in that climate I'd put the AF in there for the winter and run inhibited water during the boating season, and when I changed back to the water I'd drain and KEEP the AF. Basically, the AF would be a "storage" solution only - and the rest of the time sit in my garage.
