Hey Early Bird,
Page 1-50 in the chilton 1974-84 mercedes book, under engine coolant.
"A 50/50 mixture of water and anti-freeze serves as coolant for MB engines. Generally tap water meets the requiments for water. It is important you do not use sea water, brackish water, brine, or industrial waste waters. Also lime-free water, completely distilled water, rain water, or desalinated water should not be used, as this will only hasten the corrosion process.
In addition, an emulsifying corrsion inhibitor should be used every time you change the coolant."
The term "generally" and "completely distilled" kind of add to the confusion but if I was you I think I would start a new thread asking some of these guys with more knowledge what the real story is.
If you do start the thread, please leave a link to it here so I can follow.
