An air guide collects air from a grille located at the front of a vehicle engine compartment to a vertical radiator located in the engine compartment and which is fixed to a vehicle chassis. The air guide includes a main casing including an upper casing and a lower casing. The upper and lower casings include an opening toward the front to receive the air. The lower casing includes at least one substantially horizontal lower wall and two substantially vertical lateral walls. The lower casing axially and transversely abut the rear portion of the lower casing of the air guide relative to the chassis of the vehicle, at least in a lateral region of the lower casing, and a local structure for controlled preferred compression of the walls of the lower casing, at least in a lower portion of the lateral region of the lower casing.