1998 Buick Riviera Owner's Manual - Page 222

Adding only plain water to yourcooling system can bedangerous. Plain water, or some other liquid likealcohol, can boil before the proper coolant 'mixture will. Your vehicle'scoolant warning systemis set for the proper coolant or mixture. With plain water the wrong mixture, your engine could too hot butyou wouldn't get get the overheat warning. Your engine could catch fire and or otherscould be burned. you Use a 50/50 mixture of clean water and DEX-COOL@coolant. I NOTICE: I n cold weather, water can freeze and crack the engine, radiator, heater core and other parts. Use the recommended coolant and the proper coolant mixture. You can be burned you spill coolanton hot if engine parts. Coolant contains ethylene glycol and it will burn if the engine parts arehot enough. Don't spill coolanton a hot engine. is When the coolant in the coolant recovery tankat FULL COLD, start your vehicle. 5-17