Dexron Antifreeze mixing

"The company, however, stated that in agreeing to settle, they don't admit any liability and that they believed that Dex-Cool protected engines for longer periods than traditional coolants. Company spokespersons said that the coolant caused less wear on certain engine parts and provided various environmental benefits. They also claimed that owners who experienced engine and cooling system problems had not followed maintenance instructions. "

The only thing I have ever seen from GM on mixing coolants was that is acceptable to mix them BUT that it degrades the Dex-cools "Extended Life" and meant that you needed to switch to the maintenance intervals for the green coolant.

99% of the "coolant caused" gasket failures are NOT due to the coolant. They are due to the piss poor gasket design combined with the poor clamping of the parts. The SBC didn't have gasket failure issues till the switch to the Gen 2 head/intake designs. Many people claim the 4.3 / 5.7 intake gasket failures are due to Dex. Nope they are due to plastic gaskets and lack of even clamping forces.