1998 Oldsmobile 88 Owner's Manual - Page 210

I Adding only plain water your cooling system to can be dangerous. Plain water, some other or liquid like alcohol, boil before the can proper coolant mixturewl.Your vehicle's coolant il warning systemis set for the proper coolant mixture. With plain water the wrong mixture, or your engine could get too but you wouldn't hot 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. ~~ ~ ~ ~~~ NOTICE: In cold weather, water can freeze crack and the engine, radiator, heater core and other parts. Use the recommended coolant the proper and coolant mixture. You can be burned if you spill coolant on hot engine parts. Coolant contains ethylene glycol and it will burn if the engineparts arehot enough. Don't spill coolant on a hot engine. When the coolant in the coolant recovery tank the is at FULL COLD mark, start your vehicle.