[HummerMann]

I'm not sure if GM still uses Dex-Cool in the 2008 and newer models, but you never want to mix the green stuff with Dex-Cool. There are several states with class action suits in the works concerning GM and Dex-Cool. Although GM says it's been tested and the suits are without basis, it's been known to eat up gaskets. There's also evidence of it eating radiators and clogging them when mixed with the green stuff and even the red stuff.
Prestone® Extended Life Antifreeze/Coolant is compatible with ANY antifreeze/ coolant – regardless of color – for use in ALL makes and models of cars and light duty trucks. They even say in their literature that it is compatitble with GM Dex.