GM has used Dex-Cool for years. It's an orange color, and whoever told you not to mix them was correct. DO NOT mix them.
This guide will show you how to change it step by step.
The cooling system in your vehicle is filled with DEX-COOL engine coolant. This coolant is designed to remain in your vehicle for 5 years or 150,000 miles (240 000 km), whichever occurs first, if you add only DEX-COOL extended life coolant.
A 50/50 mixture of clean, drinkable water and DEX-COOL coolant will:
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.
WHAT TO USE
Use a mixture of one-half clean, drinkable water and one-half DEX-COOL coolant which won't damage aluminum parts. If you use this coolant mixture, you don't need to add anything else.
CAUTION: Adding only plain water to your cooling system can be dangerous. Plain water, or some other liquid such as alcohol, can boil before the proper coolant mixture will. Your vehicle's coolant warning system is set for the proper coolant mixture. With plain water or the wrong mixture, your engine could get too hot but you would not get the overheat warning. Your engine could catch fire and you or others could be burned. Use a 50/50 mixture of clean, drinkable water and DEX-COOL coolant.
NOTICE: If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost would not 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, check your cooling system.
NOTICE: If you use the proper coolant, you do not have to add extra inhibitors or additives which claim to improve the system. These can be harmful.
Wednesday, December 19th, 2007 AT 10:47 PM