I found this article to be very helpful. It even shows you how to mark the Prestone antifreeze tester to get a 35%/65% antifreeze/water ratio. I found that all three of my cars had too much antifreeze. Thanks Jim.

http://pages.prodigy.net/jforgione/MB_WW.html

__________________
1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles