1999 Oldsmobile 88 Owner's Manual - Page 240

yellowblue NOTICE: If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost wouldn't be covered by your warranty. Too much water in the mixture can freeze and crack the engine, radiator, heater core and other parts. If you have to add coolant more than four times a year, have your dealer check your cooling system. Checking Coolant NOTICE: If you use the proper coolant, you don't have to add extra inhibitors or additives which claim to improve the system. These can be harmful. The vehicle must be on a level surface. When your engine is cold, the coolant level should be at FULL COLD or a little higher. When your engine is warm, the level should be up to FULL HOT or a little higher. 6-22