DEX-COOL® is an ethylene-glycol coolant that was developed to last for 150,000 miles (240,000 km), or 5 years, whichever occurs first. It is recommended that only DEX-COOL® be used when coolant is added or changed. It's a good idea to purchase a gallon container or two of DEX-COOL® from an authorized GM dealer so the correct antifreeze is always available. A 50/50 mixture of this ethylene-glycol coolant and water should be used, providing freezing protection down to -34°F (1°C), boiling protection to 265°F (265°C), and rust and corrosion protection for the system. A solution stronger than 70% antifreeze is not recommended and pure antifreeze will freeze at only -8°F (-22°C).
A pressure vent radiator cap is used on all models to allow a buildup of 15 psi in the cooling system. This pressure raises the boiling point of coolant to approximately 262°F. at sea level. DO NOT remove the radiator cap to check the engine coolant level.
Always check the coolant level by looking through the "see through" area of the coolant recovery reservoir. Coolant should be added ONLY to the reservoir, after the system cools. Because a radiator cap, loosened when the engine is hot, will cause a loss of pressure and immediate coolant boiling, possibly with explosive force, most car makers, including GM, have designed the radiator cap in such a way that it is not easy to get a grip, to discourage inadvertent removal. Embossed on the cap is a caution against its being opened and arrows indicating the proper closed position. During routine maintenance, ALWAYS check the coolant level (and add, if required) at the coolant recovery reservoir. Refilling coolant at the radiator should only be required if the radiator and/or the cooling system has been drained.