new here, but i will give my 2 cents. from what i have heard and seen it does brake down rubber seals. i have done intake gaskets on more then few gm cars and trucks. i was told by a guy that worked at a firestone, that they would (and if you want to change it to green) that you have to do a complete flush to get all the dex cool out. then you can fill it to the green, or gold. the dex cool is to last 100000 miles.