1995 Buick Regal Owner's Manual - Page 226

Adding Coolant I NOTICE: If you usean improper coolant mix, your engine could overheat and be badly damaged. The repair cost wouldn't covered by your be warranty. Too much waterin the mix can freeze and crack the engine, radiator, heater core and other parts. To Check Coolant When your engine is cold, the coolant levelshould be at the COLD mark or a little higher. When your engine is warm, the levelshould be up to the HOT mark or a little higher.