The inside of the car smells of gas.
Mercedes came out with a service bulletin on June 10, 2015 for a fuel odor in the car. The problem is at the top of the tank where the fuel pump is serviced. The warranty was extended on these parts, but it did not state how much. I would call your local Mercedes dealer, and find out if your car is still covered. The reference number for the bulletin is: P-B-47.10/63C