A good quality windshield washer fluid is necessary not only to help clean a dirty windshield and prevent icing in freezing temperatures but to reduce the possibility that mold or fungus will grow in the tank and slime up the pump filters. If you decide to mix your own, I recommend using distilled water to reduce the possibility that chemicals in municipal water supplies will also add their own gunk to the system. A few $$'s of fluid should last the average driver several months. I too like the smell of the BMW fluid and
my dealer tops off my car at any service. It also cleans great and handles temps below "0".
That's my story and I'm stickin to it!
