With fuel consumption at the top of most new car buyers' priorities, manufacturers are sinking countless millions into developing new and innovative ways of making their models leaner, cleaner and greener.
Citroen's answer to the ultra-high mpg car is this, the C4 Cactus Airflow 2L – to give it its full and not-so-snappy title – which will return a claimed 141mpg.
This impressive figure is down to a number of factors, not least the brand's Hybrid Air system, which sees a three-cylinder 1.2-litre petrol engine (already offered in the Cactus range) mated to a hydraulic air pump and air storage tanks in the rear of the car. This compressed air is then used to pressurise hydraulic fluid which in turn can power the driven wheels.
Aside from this innovative and frugal engine setup, the Airflow Concept goes a lot further to maximise efficiency. Citroen has gone to great lengths to improve the standard model's aerodynamics, ensuring it cleaves through the air with the least amount of fuel-sapping resistance. Amongst the revisions are active flaps in the alloy wheels and flaps in the bumper that continually adjust to maximise cooling while minimising turbulence.
A number of exotic lightweight materials are also used in the car's construction, including a cocktail of aluminium and steel for the underpinnings and carbon-fibre for the Cactus's signature 'air bumps'. Overall 100kg has been saved.
The Cactus also sits on low-rolling resistance tyres to further boost economy. Overall Citroen claims the body changes alone improve the car's efficiency by 20 per cent over the standard version.
The C4 Cactus Airflow 2L was a response to a French government challenge to create a car capable of returning 141mpg by 2020. Expect to see it showcased at the Paris motor show next month, alongside similarly frugal concepts from rival French manufacturers Peugeot and Renault.
Click play on the video below to see the Cactus Airflow's aerodynamics in action.