Cadillac 1994 DeVille Owners Literature page 243

How to Add Coolant to the Coolant Recovery Tank
If you haven't found a problem yet, but the coolant level isn't at or near
"FULL COLD" on the coolant recovery tank, add a 50/50 mixture of
clean water (preferably distilled) and a proper antifreeze at the coolant
recovery tank. (See "Engine Coolant" in the Index for more ififormation
about the proper coolant mix)
C-
NOTICE:
In cold weather, water can freeze and crack the engine, radiator,
heater core and other parts. Use the recommended coolant.
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