 The XF's body was developed using computational fluid dynamics (CFD) before wind tunnel testing.Every area from the outer skin to the lightweight, composite undertray to the cooling airflow (even the shape of the exterior mirrors) was optimised using this process.The higher, squarer tail is more efficient aerodynamically than a lower, rounded one, and the XF's coupé-like roofline and raised bootlid lip improve airflow over the rear of the car.