Maybe I should change my question to "does anyone add soap to their wiper fluid?"

I found this from Mr. Gilly...

...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.

So then my questions become:

-is it really one tube of the concentrate per gallon of wiper fluid, or should it be just a few drops and,

-assuming the MB stuff is not cost efficient, what soap is good to add to the wiper fluid?

__________________
Michael

1988 300 SL (5 Speed)
1994 E320 Wagon
1997 C230