1998 Buick Riviera Owner's Manual - Page 263

NOTICE: If you use an improper coolant mixture, your engine could overheat be badly damaged. and The repaircost 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. Checking Coolant If you have to add coolant more than four times a year, have your dealer check your cooling system. 1 NOTICE: If you use the propercoolant, you don't have to add extra inhibitors additives which claim to or improve thesystem. These can be harmful. The engine coolant recovery tanklocated on the is driver's side of the engine compartment. When your engineis cold, the coolant level should be at FULL COLD or a little higher. When your engine is warm, the level should be up FiLJLLHOT or a to little higher. 6-22