1998 GMC Suburban Owner's Manual - Page 319

What to Use Use a mixture of one-half c'1e'~m t e r (preferably w distilled) and one-half DEX-COOL@ coolant which won't damage alu~ninum parts. If you use this mixture, you don't need to add anything else. NOTICE: If you use an improper coolant mixture, your engine could overheat andbe badly damaged. The repair cost wouldn'tbe covered by your warranty. Too much water in the mixture can freeze and crack the engine, radiator, heater core and other parts. Adding only plain water to your cooling system can be dangerous. Plain water, or some other liquid like alcohol, can boil before the proper coolant mixture will. Your vehicle's coolant warning system is set for the proper coolant mixture. With plain wateror the wrong mixture, your engine could get too hot but wouldn't you get the overheat warning. Your engine could catch fire and you or others could be burned. Use a 50/50 mixture of clean water and DEX-COOL@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,you don't have to add extra inhibitors or additives which claim to improve the system. These can harmful. be