I had a heater core go bad in my 99 blazer and in browsing the net i saw alot of people claiming the problem was the dexcool (orange) antifreeze. What do you guys think of dexcool? anybody changing antifreeze to something else. I understand that ethylene glycol (green) antifreeze should not be used in engines with aluminum block or head but my BMW 740 has it from the factory.