Use the official Mercedes fluid. It is concentrated so you must add water.
There are several things you can do to prevent windshield streaking. This topic has been covered many times in the past so use the "search" function in the upper right corner of this page to learn more. Also this is really a "Detailing" topic not a "Tech Help" topic.
Here are some ideas:
1) Change your wiper insert each spring
2) Thoroughly clean your windshield before washing your car. Use something like Bon Ami which is a slightly abrasive cleaner made for cleaning pots and pans. Find it in the grocery store. The #1 reason for streaking windshields is a dirty or oily windshield. I often find that Windex will not eliminate the road grime and oils like Bon Ami will.
3) Clean your wiper blade each time you buy fuel. Use windex or something similar on a paper towel to wipe the surface of the blade clean. The #2 cause of streaking windshields is a dirty blade.
4) Consider using Visionblade or Rain-X on your windshield. Rain-X works great when it's fresh but gets really bad when it starts to wear out. Visionblade ages more gracefully.
5) When you do clean your windshield with Windex or something similar, be sure to do a final polishing with a completely dry paper towel or newspaper.
Hope this helps.
Bill Wood - Webmaster
MB Autowerks Inc