The muscle cars as you knew it is dead and gone. The new generation of American muscle cars are so technologically-advanced and so sophisticated, they can beat European sports car at their own game. Take the new 2015 Ford Mustang, for example. Every bit of this new model is engineered to perfection.
Every once in a while Ford shed some lights into the details of their latest pony car, making you marvel at the how clever this thing is, but also miss the raw simplicity of the old muscle cars. This time they discuss the aerodynamics of the new Mustang, which makes it the sleekest and most aerodynamically-efficient car of its type.
The aerodynamic design of the 2015 Ford Mustang incorporates front-wheel aero curtains that help guide airflow across the front wheels. Vertical slots in the outer edge of the front fascia channel air from the front of the car to openings in the wheel wells, directing it across the outer surface of the wheel and tire. The upshot of all this is that it reduces drag, making the car more stable, which in turn improves the handling.
By making the car more slippery, a more causal term for aerodynamic, it will cut through the air more easily, meaning you need less power to achieve a certain level of performance. That is how aerodynamics help with the performance and fuel economy.