We are the second owner of the vehicle and have taken good care with regular maintenance and inspections, however we used GM's DexCool OAT antifreeze coolant (orange) as recommended by the manufacturer which slowly deteriorated the gaskets and finally dumped coolant into the cylinders. For about a year the coolant had to be occasionally topped off, I figured a small external leak and added stop leak and the problem abated. There was no indication from the oil that the gasket failed or was failing. Then without notice the car wouldn't accelerate, it had only been on for 5 minutes so no overheating, and barely managed to get home. Turned engine off and found the coolant was very low - puzzling at the time since I had just checked about two weeks earlier. Idiot light did not come on. The car wouldn't even crank - hydrolocked and fouled plugs. Mechanic had to clean plugs, change gaskets, flush radiator and replace with less corrosive coolant. If you are using DexCool, my advice is to get it completely flushed and replaced with regular antifreeze/coolant.