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Fuel efficient cars are typically pretty boring but Citroen is trying to change that with the C4 Cactus AIRFLOW 2L concept.

Currently on display at the Paris Motor Show, the concept features a number of aerodynamic styling tweaks to reduce drag by up to 20 percent. Starting up front, there's a new front bumper with three air intakes that automatically open to cool the engine and then close to improve aerodynamics. The concept also has a larger rear spoiler, side view cameras and 19-inch active shutter wheels with ultra-low rolling resistance tires.

Designers were also able to cut 100 kg (220 lbs) of weight by using materials such as aluminum, composites and high-strength steel.

Despite all the aforementioned modifications, the real coup de grâce is the Hybrid Air powertrain that consists of a three-cylinder PureTech petrol engine, a compressed air energy storage unit, a hydraulic pump/motor and an automatic transmission with an epicyclic gear train. The system operates in three different modes - air only, petrol engine only and a combination of both - and allows the concept to return an impressive 2 L/100 km (117.6 mpg US / 141.2 mpg UK).