1995 Buick Roadmaster Owner's Manual - Page 198

How to Add Coolant tothe Coolant Surge Tank If you haven'tfound a problem yet, but coolant level the isn't at FULL COLD, add 50/50 mixture of clean a water (preferably distilled) and a proper antifreeze at the coolant surgetank,but be s u e the cooling system, including the coolant surge tank pressure cap, is cool before you do it. (See "Engine Coolant"in the Indexfor more information about proper coolant mix.) the 5-14