Some information I found a while back below from...ehhh, another site. Hope you find it useful.
Bottom line. If you have distilled water, fine. Tap water in LA should be just as good.
The MB service manual states a mixture of "55%water and 45% antifreeze" is
added at the factory for year round use. No mention of using distilled water.
The manual also states;"losses caused by evaporation can be compensated by
adding tap water.
Bill Lewallen; Lexington,Ky.
MB Section 1.2.1 Fresh water specifications/treatment
Clean water which is not too hard, should be used for processing the
coolant. Drinking water frequently, but not always, satisfies the desired
Not suitable are seawater, brackish water, brines and industrial waste
water. The content of dissolved substances in the water may differ very
greatly depending on its origin (ground water, spring water, surface water)
and is of particular significance for the occurrence of corrosion.
Water which is too hard is detrimental because of the possible formation of
scale or sludging. Salt contents, primarily chlorides, greatly promote
corrosion. If doubt exists, the water should be analyzed. Information
regarding the quality of drinking water can be obtained from the local
water works or the water supply company on request. If no information is
available regarding the quality of the water, distilled or fully
demineralized water should be used.
If the water does not satisfy the permissible analysis levels, it should be
processed in a suitable manner for even good anticorrosion/antifreeze
agents are affected detrimentally in their corrosion-protecting effect if
the quality of the water is poor. Should it not be possible to soften the
water, the water should be set to the permissible hardness by adding soft
or distilled (fully demineralized) water.
An excessively high content of chloride or total ions in the water can also
be reduced by adding fully demineralized, in other words on-exchanged or
Depending on the impurities which are present in the water, it may be
necessary to use appropriate processing methods (desalination and softening
or partial methods). Information regarding processing the water can be
obtained from the local water works or water supply company as well as from
companies and engineering offices specialized in this field.
Depending on the coolant composition, the analysis values of the water
should be within the following limits:
1.2.2 Fresh water quality with coolant composition conforming to par 1.1.1
(car and CV engines)
Total of alkaline earths (water hardness): 0 to 3.6 mmol/l (O to 200 d)*
pH value at 20C: 6.5 to 8.5
Content of chlor ions: max. 100 mg/I
Total of chlorides+sulfates: max. 200 mg/l
* Common designations for water hardness in various countries:
1 mmol/1=5.6' d=10' f--7.02' e=100 mg/kg Ca C03.10 d
(German degrees=10 dGH)=1,780
(French degrees)= 1,250 e
(English degrees)=1,79 mg/kg Ca C03 (USA hardness).
If doubt exists, contact Daimler-Benz AG, Department EP/QWB
(Betriebsstoffe), H 120, D-70546 Stuttgart.
From: David C. Allen