Driven by the planet: The latest affordable automobiles are as eco-friendly as hi-tech hybrids

Sean O'Grady lifts the bonnet on a new generation of green machines

Oil at $135 a barrel. Petrol approaching 120p a litre, diesel at almost 130p. The $200 barrel looming; here by Christmas, perhaps. Headlines about our dying planet every day. Since none of all this seems to stop us using our cars, the Sexy Green Car Show couldn't be better timed. It's on now at the Eden Project in Cornwall, and the people behind it have a refreshingly realistic view of the world. From their vast glass biome domes, home to fabulous rainforest and Mediterranean mini-ecosystems, they show no inclination to throw stones at the rest of us. Far from it. The point of the Sexy Green Car Show is that cars aren't going to go away, so why not work to make them cleaner and greener?

Why not, indeed, work to make our best-selling cars cleaner and greener? For example, a 1 per cent improvement in the Ford Focus's CO2 emissions equates to 1,200 less vehicles on the road or 1,200 true-zero-CO2 vehicles. So that's what Ford have given us – their "ECOnetic" range of Focuses and Mondeos that deliver less pollution than their untweaked brethren, but at little more cost and with no noticeable difference to the driving experience. Volkswagen and its sister brands, Seat and Skoda, have also been greening their ranges with "Bluemotion", "Ecomotive" and "Greenline" editions.

Fiat have an "Eco" Bravo now. More will follow, and this greening of mainstream models adds up to a quiet, green, revolution. Ford claims that around a 2 per cent reduction in Focus CO2 performance will deliver greater reductions in CO2 emitted to the atmosphere than the combined effect of all hybrid models currently sold in the UK, and at far lower cost. Its ECOnetic Focus, with its lean 1.6 diesel engine, delivers about a 4 per cent improvement. Volkswagen's "Bluemotion" Golf, also at the Eden show, offers a 10 per cent advance.

Cause for celebration? Why not? If they told you the price of diesel was being cut by 4 or 10 per cent you might well feel that was great news. Fuel protests would be called off; parliamentary rebellions defused; everyone would be happy. With greener cars we use less fossil fuel to make the same journeys. Much of this is down to official action, and the moving of key products into the right CO2 bands for car tax; the EU target is 130g/km for average new-car emissions by 2012. Even so, it is the car makers, rather than the oil giants or Opec or the Government, who are delivering the relief we, and the planet, need. We should give them a round of applause.

So a green car can be sexy and desirable. Among the wonders at the Eden Project this year is a tri-fuel Lotus that uses sustainable bio-ethanol and methanol. The methanol is made by sucking carbon dioxide out of the atmosphere, which sounds novel and promising. In among the gardens of Eden you'll also find a hydrogen-fuel-cell-powered Morgan. Someone wants to build an electric Range Rover, and there's a carbon-fibre hatch called an Axon promising better fuel economy than anything on the market today. Heady stuff, and all very well, but you can't pop down to the dealer and place an order for one today, which is why these greener Fords and Volkswagens matter so much. The VW Polo Bluemotion for example, will deliver 99g/km of CO2, not that far behind pure electric vehicles such as the G-Wiz, once you take pollution at the power station into account. And, of course, the Polo will be faster, safer, vastly more competent than a G-Wiz. Its three-cylinder diesel engine will return 74mpg, it's claimed, so it will help the family budget too (though the list price is a little hefty, at £12,000 plus, so check the figures if you want to buy one as a money-saving venture). Green Focuses and Golfs are almost as clean as the much-hyped Toyota Prius hybrid.

The car industry spends more on research and development than any other, and the internal combustion engine has been honed over 120 years with countless billions of man-hours and money. It has worked. Ford brought a pristine 1953 Prefect to the show, and which emits almost twice as much CO2 and many times more other noxious emissions than its descendants. Yet your 2008 Focus is faster – though heavier – safer, more economical to buy and run, and vastly more comfortable and civilised than was family transport at the dawn of our new Elizabethan Age. Electronics, catalytic converters, cleverer engineering of everything from engines and transmissions to aerodynamics and tyres, lighter components, more imaginative design and production techniques have all made a huge difference. Average new car emissions have fallen by 13 per cent since 1997 – despite all the fuss about SUVs.

With the trend towards the deeper greening of existing mainstream models, we have a vista of ultra-low emissions and high economy with little or no difference in the driving experience. Some companies are taking the initiative in greening everything, as with BMW's "Efficient Dynamics" scheme. Saab, Volvo and Ford offer bi-fuel cars that will also run on bio-ethanol, controversial as that is, and Mercedes, Citroë*and Mini offer some "stop-start" models where the car's engine automatically cuts out at the traffic lights, say, and starts up again just when you press the accelerator. Many more green tweaks, and many more green models, are promised.

So what are the green tweaks, and are they worth it? You won't notice most of them, which is good. Even the most dedicated car-spotter may miss the Golf Bluemotion's differently-shaped door mirrors, for example, and the special front grille for the ECOnetic Focus may also be missed, even by cognoscenti. From the outside, and even when driving them, you'll probably not feel upset by different gearing, changes to the electronic engine-mapping, the thinner wheels and tyres, or the absence of electric windows in the back, all typical features of the green editions of existing cars.

But Ford and Volkswagen haven't yet got around to offering "stop-start" technology. And no one seems keen to drop air-conditioning, which is heavy and saps a car's energy. We like it to too much, it would appear. Still, you can always turn it off.

As the beneficiary of a special "Green Driving Test" from the Institute of Advanced Motorists, I managed to improve my fuel consumption on a measured route by about a quarter. I was amazed. Apart from dumping unnecessary weight (from the car, not me), making sure the tyre pressures are OK, and turning off the air conditioning, it's all down to the driving.

Getting from second gear to fourth gear in one move is a good idea, as is anticipating red lights and roundabouts and "coasting" in a high gear towards them, snicking into say second at the last minute and always moving.

So the clever, green, modern motorist can do very well; 10 per cent off his fuel bill with a greener car; another 25 per cent off by driving more sensibly; it's almost as if you can beat the fuel crisis and save the world single-handed. And that's a good feeling.