The car is part of PSA Peugeot Citroen's bid to meet the French government's target of having an affordable car that drinks just 2.0 litres per 100 kilometres on the market by 2020.
Under the bonnet there's a 61kW 1.2-litre three-cylinder petrol engine that's part of a compressed air hybrid drivetrain, which also features a compressed air tank underneath the boot, a low pressure tank near the rear axle, and a hydraulic motor and pump under the bonnet.
Air in the main tank is compressed during braking or coasting, or from energy syphoned off from the petrol engine. In zero emissions mode or during hard acceleration air in that tank is decompressed to power the hydraulic pump and motor.
An automatic epicyclic transmission is able to blend power from both the petrol and hydraulic motors, as well as source power exclusively from either the three-cylinder or compressed air engine.
To help the prototype vehicle meet its 2.0L/100km target, Peugeot shaved 100 kilograms off the weight of a regular 1.2-litre 208; the 208 Hybrid Air 2L tips the scales at a spritely 860kg.
Special weight-saving measures include a new carbonfibre tailgate that only requires one strut to hold it up, and aluminium engine mounts, side members and rails. Carbon composite materials were used for the car's body panels, doors, roof and sides, as well as the suspension's coil springs.
Various external elements were reworked to improve aerodynamics. This includes a smoothed out front air intake and undercarriage, and wing mirrors replaced by slimline cameras. Unlike many hybrids, this 208 prototype rides on large 18-inch alloys, although they are unusually narrow, as evidenced by the 165/50 Michelin tyres they're clad with.
The 208 Hybrid Air 2L technology demonstrator follows on from the Citroen C3 Hybrid Air that was shown off at last year's Geneva motor show.