No, you don't have to return it to the same dealership. You can return it to any dealer in the country.
The typical mileage rate abouve your allowance is $0.20, but may be $0.25 on an M3. However, you will have no surprises as it would clearly be given to you before you sign the paperwork.
Originally Posted by masamune
Bump...anyone know the answer to these? Looking to make a decision soon. I searched and saw other cars were .20/mi, but not sure if this is across the line.