1997 GMC Suburban Owner's Manual - Page 309

What to Use Use a mixture of one-half cloun \ L u t P r (preferably distilled) and one-half DEX-COOLS coolant which won't damage aluminum parts. If you use this mixture. you don't need to add anything else. NOTICE: If you use an impropercoolant mix, your engine could overheat and be badly damaged. The repair cost wouldn't be covered by your warranty. Too much water in themix 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. ~ Adding only plain water to yourcooling system can be dangerous. Plain water,o r some other liquid like alcohol, canboil before the proper coolant mix will. Your vehicle's coolant warning system is set for the proper coolant mix. With plain .wateror the wrong mix, your engine could get too hot butyou wouldn't get the overheat you warning. Your engine could catch fire and or others could be burned. Use a 50/50 mix of clean water andDEX-COOL@coolant. I NOTICE: If you use the propercoolant, you don't have to add extra inhibitors or additives which claim to improve the system. These canbe harmful. I 6-27