1997 Pontiac Bonneville Owner's Manual - Page 279

NOTICE: If you use an impropercoolant mix, your engine could overheat and be badly damaged. The repair cost wouldn'tbe covered by your warranty, Too much waterin the mix can freeze and crack the engine, radiator, heater core and other parts. Checking Coolant If you have to add coolant more than four timesa year, have your dealer check your cooling system. NOTICE: If you use the proper coolant, you don't have t'o add extra inhibitors or additives which claim to improve thesystem. These can be harmful, When your engine is cold, the coolant level should be at FULL COLD or a little higher. When your engine is warm, the level should be up to FULL HOT or a little higher.