The International Cessna^® 170 Association

"There are many specialized products that claim supremacy in this task—including Meguiar’s Bug and Tar, Bug Off, and Rain-X. But for a single, inexpensive, widely available product that works on both windshields and airframes, it’s tough to beat plain old Pledge. "

http://www.aopa.org/News-and-Video/All- ... t/p_frugal

However, there are always naysayers:

http://youtu.be/bhlZdP1uKyc

Pledge works great as long as the windshield is warm or at least not frozen. It really makes a mess on a cold day.