I used the cheap stuff very similar to what you got. I assume it will hold up (considering the 850's been totaled once already, and I want to replace when I can afford it..) until I can upgrade... If I have to flush every 30k instead of 50, thats OK too, because it was 20/case...

The snap ring gets the zip-tie because its easier 'insurance' than getting a new clamp from the dealer. I went with an hose-clamp from lowes because I figured it'd last longer than a zip tie.. Its not a simple snap ring, you'll notice when you start. 25 degrees isn't ideal to do it, but it shouldn't be awful. Keep the fluid inside before you do it, and it might be best to drive the car till its almost warmed up to start flushing. Using autoRX i think you add like 4oz to whats already in there, as long as the fluid isn't at max you're OK. I haven't used the other treatment. If you go AutoRX, you drive another 1000 miles, perhaps you could get to an "indian summer" day when its time to flush..
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If you're not driving it "like its stolen," are you really driving?