1993 Cadillac DeVille Owner's Manual - Page 253

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 above near "FULL COLD." add a 50/50 mixture of clean water (preferably distilled) and a proper antifreeze the coolantrecovery tank. (See at "Engine Coolant"in the Index for more information about the proper coolant mix.) A CAUTION: J d i n g only plain water to your cooling system can be dangerous. Plain water, or some other liquidlike alcohol, can boil before the proper coolant mix will. Your vehicle'scoolant warning system is set for the proper coolant mix. With plain water or the wrong mix,your engine could get too hot but you wouldn't get the overheat warning. Your engine could catch fire and you or others could be burned. Use a 50/50 mix of clean water and a proper antifreeze. 1 i I 240