Vauxhall Corsa Eco

Thanks to that reduced ride height, special wheeltrims, fuel-saving tyres and a tiny roof spoiler, the company's engineers have cut the Corsa's drag coefficient. Coupled with a modified version of its 1.0-litre three-cylinder engine and a semi-automatic Easytronic gearbox, Vauxhall claims to have created the most economical petrol-powered supermini money can buy. So should rivals be worried?

The Corsa Eco will easily top 50mpg round town if you're considerate with the throttle and gearchanges. But that doesn't make it a brilliant choice for high-mileage drivers. The trade-off for all its environmental benefits is lethargic performance, with the 0-60mph sprint taking 18 seconds even if you drive the car in a very ungreen manner.

Take it gently and the Eco is far more pleasant. Despite a lack of power, it cruises ably on the motorway, the buzzy engine settling down to a refined hum, while the altered aerodynamics help cut wind noise. The Easytronic system is irritating to use, though, with manual changes seeming to take forever and automatic ones occurring randomly if you're maintaining a steady speed.

The Eco costs