Ok I just got home from the service shop.
When they flushed the radiator and I can see some rust coming out of the radiator.
I've been using the green coolant since I had the D1 and I don't seem to notice rust in the expansion tank.
But when I started using Dexcool after a month or so I noticed a thin film of rust in the insides of the expansion tank.
I say avoid Dexcool whether D1 or D2 and use 50/50 premixed green coolant with distilled water.
I also replaced the t/stat.
Cheers.

 

no one has yet to say what Dex Cool will do bad... hmmmmmm....

Have done about 15k with dex cool... no rust.... hmmmmmm...

urban legend????

 

Umm class action lawsuits...

 

I used to sell coolant. I had to take a class on our coolant and why it was better than the competion.
I have talked to 100's of mechanic's and not one of them, including GM Goodrich mechanics recommend using DexCool in anything.
The GM guys say use it as long as the car is under warrenty, once the warrenty expires flush the cooling system.
If DexCool is NOT properly maintained it becomes corrosive and eats gaskets.
Some people have good luck with DexCool, some dont.
A few years after it was first introduced there was a class action law suit here in MI against GM for clooged radiators and leaking intake manifold gaskets.
It is not a urban legand.
Just Google DexCool and do some research and then draw your own conclusion.