This study introduces an innovative approach to enhancing aerodynamic efficiency in automotive applications by exploiting shape memory alloy technology. To this end, a thorough investigation of the thermomechanical behaviour of these alloys was conducted in the paper. Using a UMAT subroutine, the pseudoelastic effect and the shape memory effect of these smart materials were analysed numerically simultaneously, allowing accurate predictions of their behaviour under different loads, and facilitating the design and optimization of devices and systems based on SMAs. Therefore, the article proposes an innovative solution to optimize aerodynamic efficiency by using a Grille Shutter with variable openings. The Active Grille Shutter uses a bistable SMA actuator, allowing two optimal opening positions for specific load conditions. These actuators hold two stable states without energy consumption, ensuring efficient and reliable operation and allowing rapid transitions between the two states, making them ideal for applications that require timely responses. By using this specially designed and numerically analysed system, it has been confirmed that suitably dimensioned shape memory springs can guarantee a movement of the blades of the 90°, allowing an improvement in vehicle efficiency of about 4% at a speed of 140 km/h.