So, I decided to find out the difference between the blue washer fluid in my Prius and the pink one in the family Camry. So I gave my local Toyota service centre a call. Their explanation is that the blue one in the Prius is pre-diluted and hence can be used as-is. The pink one they sell comes with antifreeze (the one that's good to -40). He said that I could dilute it up to 50/50 with water for summer use which is good to -20 (so he says) but he recommends not diluting it for winter.
I believe I have seen washer fluid in both colors for each temperature grade. Why they would worry about freeze grades around here, I don't know. Any one of them would more than do.
I've used several blue or pink washer fluids over the years and I think all were rated for at least 20 below. They all froze up on me on the windshield. I now use Prestone washer fluid, kind of clear yellowish, and have had much less problems with freezing.
I stocked up on Rain-X deicer (pinkish) last winter, and added some of the bug remover version (blue) last week. Kinda muddy looking now, but if a cold snap is followed by a plague of locusts, I'm covered...
I use the "Green" Prestone stuff, it cuts trhough all kinds of dirt and grime, way more than the pink or blue stuff. It lilke has scrubbing bubble sor something.
<div class='quotetop'>QUOTE(Tideland Prius\";p=\"96889)</div> The anti-rain aspect is weaker than treating your windshield directly, but it does bead up and flow off under the right conditions. As far as bug cleaning goes, it does cut through things stuck to the glass OK...