Detroit News has a piece that notes Ford's work to improve aero on the next generation Mustang:
- active grille shutters on the turbocharged version (turbo requires even more cooling area, so actively changing flow-through depending on demand makes sense)
- relocated side mirrors from the A-pillars to the doors
- slots in the fascia that redirect airflow into the front wheel arches -- "air curtains"
Results: 1% better highway fuel economy on the fastback version.
Source:
Beauty on inside of overhauled Ford Mustang | The Detroit News