Britain's cleanest cars - Executive and luxury cars

What Car? Greenest Executive and Luxury Car: Saab 9-5 BioPower

This Saab has the potential to out-green any of the winners here. On sale in the UK now, the specially adapted 9-5 can run on bioethanol distilled from plant matter, turning the CO2 dilemma from a vicious circle into a virtuous one.

It still emits carbon at the same rate as when it's running on petrol, but rather than adding to the sum of greenhouse gases, the carbon dioxide released is merely what the plants used to make the fuel soaked up in the first place.

Other than searching for biodiesel fuel, the driver does nothing differently. At just £600 extra, the sharply styled new 9-5 is a sleeper here just now. More Government incentives and filling stations could be enough to wake it.
Price: From £22,070
MPG: 32.8
CO2 emissions: 204g/km

Lexus GS450h
Is true exec muscle incompatible with environmental virtues?

The hybrid GS, which is due to be launched in May, uses a battery-backed V6 to give V8 power with four-cylinder emissions, or so says Lexus. A 35mpg target with 335bhp sounds good to us.
Price: From 38,058
MPG: 35.8
CO2 emissions: 186g/km
Exempt from London Congestion Charge

BMW 520d
This is one big BMW that doesn't shout excess. Newly launched into the range, the 520d takes the four-cylinder diesel from the 3 Series to create a parsimonious executive, with CO2 emissions of just 158g/km and an average economy figure that hits 48mpg.

The particulate filter comes as standard on the 520d, trapping virtually all the soot that usually gives diesels a bad name.
Price: From £25,925
MPG: 47.9
CO2 emissions: 158g/km