But what has absolutely convinced me is the class Entkalkerformel. I used to have with the other "normal" laundry additives, the problem that they did not prevent calcium deposits.
Consequence: Every few months the wiper nozzles were completely tight and I had to dismount always to herauszupulen the lime platelets tedious. (How have here very hard water / hardness range 4)
With Dr. Wack since I had not this problem. The lime is apparently bound for the edge of the windscreen (where the wipers do not wipe) shows a milky film when the washer fluid is dried. By the time you get used to it and it is certainly better than to go flying blind, because the nozzles are clogged.
Otherwise, I can see no better or poor washing performance compared to other cleaners.
EDIT 05/2015:
After 2 years, 250 ml bottle is empty and was enough for 2 cars in summer and winter. The mileages of both cars are each at about 14000 km / year with regular cleaning water use (usually before departure).
Now I've ordered a new bottle.
The then sufficient for the next 2 years :)