 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.The basic substructure of the XF has been carried over from the preceding S-Type, although the body has been stretched to meet crash safety requirements, and heightened to provide additional headroom while still retaining the "saloon within a coupé" proportions.The suspension and mountings are the same as that used on the XK, while the engine line-up is basically similar to that used in the S-Type.