It is an all in one cleaning additive for bleach based cleaning solutions, just one product does it all. There are lots of posts here about this point.
How does it save me money?
It boosts the bleaching ability of a sodium hypochlorite or calcium hypochlorite cleaning solution so you use less bleach. It also helps the mix to penetrait and stick to the surface.
How does it make my mix better or more efficient?
See above :)
What are the mix ratios for roof washing / house washing?
I have heard some guys say green wash can have a reaction to aluminum siding? The color fades a bit, but over a few days it comes back and looks great. Anyone else heard about this?
I have been using it for over a decade and never saw a reaction on alum siding. Id love to see some pix though and see what the reaction could be and if it may be more with the powder coat color oxidizing than the alum its self.