We already mentioned PSA's plans to downsize engines in an effort to improve fuel efficiency. The French company will showcase the progress its making during PREDIT (National Program for Terrestrial Transport Innovation), which is taking place this week in Paris. PSA will show a prototype co-developed with Valeo and IFP (the teams behind the low-carbon Smart). The prototype is a Citroën C2 with a two-cylinder engine, 8 valves and a mild-hybrid system with Stop&Start and regenerative braking. This allows the sub-subcompact to use 3.8 l/100 km (62 mpg U. S.) and emit just 90 g/km of CO2. The "regular" C2 featuring a 1.1 liter I4 engine uses 5.8 l/100 km (40.5 mpg U.S.) and produces 138 g/km of CO2. The C2 in the gallery below is the sporty version.
[Source: Autoplus (h/t to Dominique for the tip)]