2005 Pontiac GTO Owner's Manual - Page 209

How to Check and Add Fluid To check the fluid level, look at the markings on the reservoir. If the fluid level is between the MIN and the MAX line, the fluid level is correct. If the fluid level is between these marks do not remove the cap, as the fluid will quickly absorb moisture. See Engine Compartment Overview on page 5-12 for more information on reservoir location. If fluid does need to be added, first turn the vehicle off. Remove the cap and add the proper fluid. Remember to replace the cap and clean up any spilled fluid. The following explains the cooling system and how to add coolant when it is low. If there is a problem with engine overheating or if coolant needs to be added to the radiator, see Engine Overheating on page 5-26. A 50/50 mixture of clean, drinkable water and DEX-COOL® coolant will: Engine Coolant The cooling system in your vehicle is filled with DEX-COOL® engine coolant. This coolant is designed to remain in the vehicle for five years or 150,000 miles (240 000 km), whichever occurs first, if only DEX-COOL® extended life coolant is added. Give freezing protection down to −34°F (−37°C). Give boiling protection up to 265°F (129°C). Protect against rust and corrosion. Help keep the proper engine temperature. Let the warning lights and gages work as they should. Notice: Using coolant other than DEX-COOL® may cause premature engine, heater core or radiator corrosion. In addition, the engine coolant may require changing sooner, at 30,000 miles (50 000 km) or 24 months, whichever occurs first. Any repairs would not be covered by your warranty. Always use DEX-COOL® (silicate-free) coolant in your vehicle. 5-23