From the time that I purchased this car I thought that there was something not quite right about either the transmission or the engine. Switching to premium gasoline seemed to help. Then last night started out to dinner and car would not shift out of first gear and engine was revving at seemed like a very high rate. Maximum speed was approximately 3 mph. I was able to get it home and in the garage. Check engine light was on and OnStar reported: P0700 Service within 7 days The Engine and Transmission System is not performing as expected. An issue has been detected in the Transmission System that transfers power from the engine to the drive wheels. You may experience reduced power or shifting issues. If the vehicle is continually driven with the check engine light on, the emission controls might not work as well, the vehicle fuel economy might not be as good, and the engine might not run as smoothly. This could lead to future repairs. Other codes: P18AA So, the car has been towed to the dealership where it will sit until Wednesday. I hope to know more then.