My '06 came from the factory with a PS cooler. I wouldn't suspect anything wrong with the fluid your using as that stuff has had a good rep for many years now. I know a lot of people go for the lesser "lifetime warranty" part at the parts store, but trust me when I say that non of them are s good as the original AC Delco parts. That lifetime warranty doesn't mean squat if your having to change it out two or three times. Maybe hit up a local wrecking yard for a factory cooler. I'm sure someone out there has done that conversion.