I have read that certain types of antifreeze can damage the intake manifold gasket. What type/brand of coolant should I be using in my 95 Bonneville SE?

personally i think it'* just a myth they will all eventually turn to acid and eat thing that you dont want them too just use whatever is in your car now in terms of color but prestone makes good stuff
Please add the year and trim of your ride in your siganture it will help us better assit you in answering your questions
do this by going to your user cp and click on edit signature pretty straight foward from there
thank you
steve

I am a firm believer in running what the car came with.

So in your case, normal green coolant

Here is a good short article explaining different coolant.
Looks like it is put together by Napa but appears to be accurate.

Universal Coolant: The Ultimate Antifreeze?

I use Prestone.

I have dexcool in mine. It had been filled with dexcool about 6 months ago from the mechanic the previous owner knew. Would it be a good idea to flush this crap out and put in good quality green coolant? I highly doubt dexcool can last 150,000 miles.

I removed my dex last year and filled with green. Not because I don't like dex, or fear it will damage my engine. but because I like the fact that if the green drips on the ground, you can see it'* green very easy. I want all my fluids easy to identify.

Quick. Run to the garage and get that Dexcool out before its too late.

New Dex isnt old Dex. So the debate is pointless. And wont allow it to be entertained in the Forum further. I change every 3-4 years regardless. this is winter #4 for the GXP. will be flushing this coming spring. For those that want to switch, I would use Prestone universal. Neither Dex likes straight green and you'll never get all the Dex buildup out with a simple flush.

I put Prestone in my cars, along with an entire system flush to clean it out