1998 Buick Century Owner's Manual - Page 281

What to Use Use a mixtureof one-half clean water (preferably distilled) and one-half DEX-COOL@coolant which won't damage aluminum parts. If you use this mixture, you don't need to add anything else. NOTICE: If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost wouldn't be coveredyour by warranty. Too much water in the mixture can freeze and crack the engine, radiator, heater core and other parts. Adding only plain water to your cooling system can be dangerous. Plain water, some other or liquid like alcohol, can before the proper boil coolant mixturewill. Your vehicle's coolant warning system is set for the proper coolant mixture. With plain watero r the wrong mixture, your engine could get too hot you wouldn't but get the overheat warning. Your engine could catch fire and you or others could be burned. Use a 50/50 mixture of clean water and DEX-COOL@coolant. If you have to add coolant more than four times ayear, have your dealer check your cooling system. NOTICE: If you use the proper coolant, don't have to you add extra inhibitors or additives which claim to improve the system. These can be harmful. 6-21