Britain's cleanest cars - 4x4s

What Car? Greenest 4x4s: Lexus RX400h

The standard 3.0-litre version of the Lexus off-roader produces 288g/km of CO2, but the 3.3-litre RX400h reduces that by nearly 100g to become one of the greenest off-roaders you can buy.

How? This RX uses a battery-supplied power system, much like that of the Toyota Prius, to give a boost to its 3.3-litre V6 petrol engine.

The two electric motors can even take over completely at urban speeds, resulting in eerily silent motion. As with other hybrids, the battery pack is recharged via braking and this helps to improve economy – from the RX300's 23mpg to nearly 35mpg.

Otherwise, it's the same well-equipped, five-seat 4x4 as its conventional brother, except that the combined battery/V6 kick cuts the 0-62mph time to 7.6sec.
Price: From £36,393
MPG: 34.9
CO2 emissions: 192g/km

BMW X3 2.0d
BMW's beefy but frugal 2.0-litre diesel elevates another model to the winners' rostrum: this time, the X3.

Its 191g/km is excellent for a 4x4 and it manages a 39mpg average. It also gets a particulate filter as standard.
Price: From £28,560
MPG: 39.2
CO2 emissions: 191g/km

Toyota RAV4 2.2 D-4D (180)
Another Toyota, but this time the new RAV4 uses a conventional diesel engine and filter to give low CO2 emissions and economy. Its 185g/km beats even the two-wheel-drive Nissan X-Trail's.

The most powerful (and priciest) RAV4 uses a clever diesel filter that cuts emissions of particulates and poisonous oxides of nitrogen (NOx).
Price: From £27,015
MPG: 40.4
CO2 emissions: 185g/km