Since you have petcocks on the block I would drain and catch it so you can reuse it, I seen its $28 a gallon.... Flush the system out with water and fill with 50/50 antifreeze.

Repeat in the spring and put the blue back in.

I question just how detrimental it would be to mix regular antifreeze with it. Probably wouldn't hurt anything but at $28 a gallon I am running it through a filter and saving it.