An assembly is provided for maximizing cooling and fuel economy. A grille opening in the vehicle allows air to flow toward the engine compartment along a first path and a bottom breather opening allows air to flow toward the engine compartment along a distinct, second path. An air separator extends between the first and second paths to prevent mixing of airflow along these paths. The air separator may be a thin dividing wall of a deformable material that extends toward a condenser/radiator assembly at low vehicle speeds. At increased vehicle speeds, the deformable portion deflects to enhance airflow along the second path. An associated method of controlling airflow includes terminating the air separator closely adjacent a condenser/radiator assembly to limit mixing of airflow along separate paths, and deflecting in response to increased air flow to alter airflow through at least one of the first and second paths.