1998 Cadillac DeVille Owner's Manual - Page 310

What to Use Use a mixture one-half clean water (preferably of distilled) and one-halfDEX-COOL@coolant which parts. If you use this mixture, won't damage aluminum you don't need add anything else. to NOTICE: If you use an improper coolant mixture, your engine could overheat be badly damaged. and 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. I Adding only plain water your cooling system to can be dangerous. Plain water, some other or liquid like alcohol, can boil beforeproper the coolant mixturewill. Your vehicle'scoolant is warning system set for the proper coolant mixture. With plain water the wrong mixture, or your engine could get too hot you wouldn't but 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. NOTICE: I you usethe proper coolant, don't have to f you add extra inhibitors or additives which claim to improve the system. These can be harmful. 6-23