A car having a frame, which supports a pair of front wheels and a pair of rear wheels, a passenger compartment, at least one pair of doors, and an underbody which delimits the car on the lower side, faces the road surface, and has an aerodynamic diffuser, which is arranged in a rear position and is provided with a chute having a height with respect to the road surface that progressively increases when longitudinally moving from the front to the rear. The underbody can include a pair of aerodynamic channels, each of which extends longitudinally, leads to the aerodynamic diffuser, is open on the lower side towards the road surface, has a shape of an upside-down “U” in its transverse section and is open underneath towards the road surface and has, in its transverse section, an area that progressively increases when longitudinally moving from the front to the rear.