The Insider: The Fiesta goes green and makes a splash

There was a time when choosing to buy a green car simply meant deciding on a automobile that was available in a particular paint colour: a humble lime Mini, perhaps, or a Jaguar decked out in traditional British racing green. But we now live in an age when a documentary about global warming can win an Oscar and the question of carbon footprints is increasingly one of the most important things a car buyer can consider.

This is not only because modern motorists have suddenly found an ecological side to their conscience. The cost of oil may have tumbled in recent weeks – leaving the managers of petrol stations with some breathing space before having to worry about a lack of digits on their giant forecourt pricing signs again – but helping to preserve the environment still means preserving the petrol pounds in your pocket, too.

It is no mere coincidence, then, that one of the best value cars on the market has "eco" in its name. The Ford Fiesta Econetic has recently been declared the best value green car by the consumers' group Which? and, according to its manufacturers, offers a fuel consumption rate of 76.3mpg. What's more, its 1.6 litre, turbo diesel engine produces the lowest carbon emissions of all mass-produced cars on sale in Britain, at 98g/km. And by falling below the 100 mark, the Fiesta Econetic scrapes into Band A of Vehicle Excise Duty – meaning it's free of road tax. The most basic three-door model retails at £11,845, while the five door variety begins at £600 more.

For some readers, the word "diesel" might have stood out back there. However, the general consensus is that diesels no longer deserve their old reputation for offering a less rewarding driving experience and growling like a Rottweiler with a sore throat; in fact, some would argue modern diesels make for a nicer drive than their petrol rivals.

Fairer to consider is the stubborn factor that, although diesel engines are more economical, petrol remains noticeably cheaper at the pumps. If this means petrol still wins your vote, the Suzuki Splash, according to Which?, is the next best value alternative.

The Splash comes with a 1.2-litre, 86bhp four-cylinder engine, although there is also a 1.3 litre diesel model available. Its carbon emissions are less impressive than the Fiesta Econetic, its 131g/km placing it in Band C of VED. This translates to an annual charge of £120. However, this little car maintains its value for money thanks to a spacious interior, and even the basic model offers a wide array of modern features. These include air conditioning, remote central locking and an electronic stability programme to prevent skidding during emergency manoeuvres. All in all, the Splash is worth a look at £8,999.

What to look out for: Questions to ask yourself

Where will the car be used?

There can be big differences in a car's fuel efficiency depending on whether you're predominantly a city driver or someone more often found on the motorway.

Diesel or petrol?

Diesel models are more expensive to buy and their fuel is more costly. But diesels are more economical, so if you tend to drive a high number of miles at optimum fuel consumption, they can work out cheaper in the long run.

What tax band does it fall under?

There are now seven bands of Vehicle Excise Duty according to emission levels, ranging from zero to £400 per year.

What's the real fuel consumption rate?

The official figures don't always match up with reality on the road, so check independent guides for a better idea of exactly what the hit to your pocket and the environment might be.

The Insider is written in conjunction with the consumers' group Which?. For more information on the best green cars visit their website www.which.co.uk/cars or buy a copy of the 'Which? Complete Guide to Greener Driving' at high street retailers for £6.99. To get three issues of 'Which?' magazine for £3, call 01992 822800 and quote INADVICE.