Such is the case of Citroën with its Airdream label, which was seen in the C5 during the EVER Green Car Salon in Monaco last week. The C5 is a medium-sized sedan, about the size of a Mercedes E-Class, which is mated to PSA's well-known 1.6 HDi engine good for 110 HP. This allows the car to run 42 mpg US (5.6 l/100 km in mixed European cycle) and produce 149 g/km CO2. As most diesel PSA powertains, it accepts a mixture of up to 30 percent of biodiesel . Unfortunately, although it's a nice car, it can't compete with the original concept.