1995 Cadillac Seville Owner's Manual - Page 256

How to Add Coolant to the Coolant Surge Tank If you haven't found aproblem yet, but thecoolant level isn't at a visible level within the surge tank, adda 50/50 mixture of clean water (preferably distilled) and a proper antifreeze at the coolant surge tank, but be sure the cooling system, including the coolant surge tank pressure cap,cool is in before you do it. (See "Engine Coolant" the Index for more information aboutthe propercoolant m x ) i. - 5-17