1998 Oldsmobile 88 Owner's Manual - Page 250

NOTICE: When adding coolant, is important that you it use onlyDEX-COOL@(silicate-free) coolant. If coolant other than DEX-COOL is added to the system,premature engine, heater core or radiator corrosion may result.In addition, the engine coolantwill require change sooner at 30,000 miles (50 000 km) or 24 months, whichever occurs first. Damage caused the by use of coolant other than DEX-COOL@ is not covered by your new vehicle warranty. What to Use Use a mixture one-half clean water (preferably of DEX-COOL@coolant which distilled) and one-half won't darnage aluminum parts. If you use this mixture, you don't need to add anything else. -- Adding only plain water your cooling system to can be dangerous. Plain water, some other or liquid like alcohol, can boil before proper the coolant mixturewill. Your vehicle's coolant warning system is set the proper coolant for mixture. With plain water the wrong mixture, or 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 waterand DEX-COOL@coolant. 6-21