2008 Buick Enclave Owner's Manual - Page 330

How to Add Coolant to the Coolant Recovery Tank Notice: This vehicle has a specific coolant fill procedure. Failure to follow this procedure could cause your engine to overheat and be severely damaged. If you have not found a problem yet, check to see if coolant is visible in the coolant recovery tank. If coolant is visible but the coolant level is not at or above the FULL COLD mark, add a 50/50 mixture of clean, drinkable water and DEX-COOL® coolant at the coolant recovery tank, but be sure the cooling system, including the coolant recovery tank pressure cap, is cool before you do it. See Engine Coolant on page 5-22 for more information. {CAUTION: Steam and scalding liquids from a hot cooling system can blow out and burn you badly. They are under pressure, and if you turn the radiator pressure cap - even a little - they can come out at high speed. Never turn the cap when the cooling system, including the radiator pressure cap, is hot. Wait for the cooling system and radiator pressure cap to cool if you ever have to turn the pressure cap. 5-30