Best in Class

Best in class:
smart fortwo CDI - 86g/km

Best of the rest:
Toyota iQ 1.0 - 99g/km
Nissan Pixo 1.0 - 103g/km
Suzuki Alto 1.0 - 103g/km
smart fortwo MHD - 104g/km

Because they are small and light, city cars have, on average, the lowest CO2 outputs of any class. Best of all is the smart fortwo diesel, which at 86g/km is by far the class leader with much lower emissions than the rest of the segment. Small car designers rely on attributes such as compactness and light weight to produce good fuel consumption and low emissions, as the cars are too cheap to have much in the way of high-technology. The smart micro hybrid drive is the only car here with anything other than a standard small petrol or diesel engine and sports a start-stop system to give it a low CO2 output.