You bought used, and 1st question that should come to mind is how was this car previously used and what was done to vehicle before you. Gm pulled up quite the history on it ,and rental use . The rental use is most concerning and is unpredictable as no one knows what rentees did to it. As another user put its a roll of the dice. There were probably flags to the prior owners that motivated them to sell it. I had friend who never changed his oil once because he never intended keep the vehicle that long. I empathize with you in this situation. You may want seek some legal advice if your out $64000