I think you're mistaking what MB is telling you to use. You are supposed to use "commercially available", aka "store-bought" washer solvent of your own choosing, and they want you to add this "Concentrate S" (there also used to be "Concentrate W" also, but they are both now replaced by a single product, "VR" and 4 numbers.....9022?). MB doesn't sell washer solvent, just this concentrate, which is basically a soap product which they say will improve the cleaning of the wipers.

Gilly