1998 Chevrolet Express Van Owner's Manual - Page 262

NOTICE: I you use an improper coolant mixture, your f engine could overheat and be badly damaged. 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. NOTICE: If you use the proper coolant, don't have to you add extra inhibitors or additives which claim to improve thesystem. These can be harmful. When your engine is cold, the coolant level shoiAd be at FULL COLD, or a little higher.