1998 Oldsmobile Achieva Owner's Manual - Page 250

NOTICE: When adding coolant, it is important that you use only DEX-COOL' (silicate-free) coolant. If coolant other than DEX-COOL isadded to the system, premature engine, heater core or radiator corrosion may result.In addition, the engine coolant will require change sooner at 30,000 miles (50 000 km) or 24 months, whichever occursfirst. Damage causedby the use of coolant other than DEX-COOL' is not covered by your new vehicle warranty. What to Use Use a mixture of 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. -- Adding only plain water to your cooling system can be dangerous.Plain water, or some other liquid like alcohol, can boil before proper the coolant mixture will. Your vehicle's coolant warning system isset for the proper coolant mixture, With plain water or 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 beburned. Use a 50/50 mixture of clean water and DEX-COOL@coolant, 6-22