Smart Eco

Small, light and efficient – Smart is the clever choice for green motorists.

In fact, its ForTwo city car is one of the cleanest new models you can buy. The recently launched turbodiesel version is powered by a three-cylinder 799cc direct-injection engine, mated to a five-speed semi-automatic gearbox. As a result, it claims CO2 emissions of only 88g/km and incredible fuel returns of 85.6mpg.

But the trade-off will be performance, as the car delivers a tiny 54bhp power output.

Buyers looking for more punch should consider the 71bhp 999cc petrol version, which comes with micro hybrid drive (mhd). This is essentially stop-start technology that cuts the engine as you roll to a stop, before firing it up again when you lift off the brake pedal. The mhd also incorporates a kinetic energy recovery system that tops up the battery when coasting and braking.

This kit cuts CO2 emissions to 103g/km and boosts economy to 65.7mpg. But compared to the bigger and heavier Ford Fiesta ECOnetic – which manages 98g/km and 76.3mpg – these figures are a little disappointing.

However, Smart is ready to hit back with a zero-emissions ForTwo. Since 2007, electric-powered versions of the city car have been on trial in the UK with fleet customers. The plug-in model has been developed in conjunction with UK motorsport specialist Zytek, and promises a range of up to 72 miles from a single, eight-hour charge. A production version is expected in showrooms in 2012.

BEST ECO BUY: Fortwo diesel