My husband put in a tank of mid grade gas versus the premium. I have read the threads dealing with the octane issues, but I really need someone to tell me that I don't need to take the car to the dealership. It has the loss of power mentioned, which I hate. It has a slight shudder when stopped and idling. Honestly I feel like I could just smack my husband, he's a great guy, but dangit! By the way the car is a 2004 C230 kompressor sport sedan. I use it to run the kids around to their various activites and don't want it to conk out with my kids in the car and get stuck on the side of thr road. Thanks to anyone who can soothe me, or point me in the right direction.