Martin Love

SULKING ON the road outside my house, listing slightly as if carrying an old shoulder injury, is a large grey Volvo estate. It has no hub caps they were stolen months ago and the rear windscreen wiper, like a drooping tulip, hangs downwards so that the only thing it cleans is the number plate. Where once there was gleaming paintwork, there is now just a crisscross of scratches and white keylines, as if the car was a self-harmer in some traumatic earlier life.

My car is 10 years short of being a classic and 14 years long of being showroom fresh. It cost me the equivalent of $3,100 three years ago and it has just clocked up its 240,000th km that's more than halfway to the moon. But its glory days are behind it and I don't know whether to replace it or keep it limping on...

Why don't you just buy a new car, ask my incredulous neighbours, as they watch it oozing brake fluid on to the street. I make the usual excuses: it's so practical, you can leave it anywhere... The neighbours nod, knowing full well that the truth is, I can't afford a new one.

But now I have a new excuse. "I'm keeping it because it's environmentally friendly..." Surely not, they gasp. How can an emissions-belching, gas-guzzling old trooper possibly compete with, say, a Prius or a Honda Civic?

Consider the three Rs, I say, the creed of the ethical movement: reduce, reuse, recycle. Keeping an old car going fits the ethos perfectly.On the other hand, buying a modern car means you'll have a more efficient, cleaner product. Stringent exhaust limits known as Euro 4 have seen emissions fall to the extent that a car built today produces 20 times fewer local pollutants than one made 30 years ago. So at what point does it become more eco-efficient to buy a new car than to keep your dodgy old one running? "It's complicated, and depends on which pollutants you want to reduce," says Ben Lane, a leading environmental consultant( . "If you look at the carbon emissions produced during an average car's lifecycle, only 10 per cent are created in the vehicle manufacturing process, 10 per cent are created producing the fuel and getting it to garages, and the remaining 80 per cent are emitted during the vehicle's use."

A tremor enters my voice: "So has my car become an eco-liability?"

"It also depends on your mileage," Dr. Lane adds. "If you have an old small car that does 14 km per litre or better and you cover less than 6,500 km a year, and you live in the country, then I'd keep it. But if you are a high-mileage driver and live in a city centre, then trade up to a newer model with good fuel economy."

Gulp... that's me. But is there nothing I can do to "green my ride"? The U.K.'s Society of Motor Manufacturers and Traders says that if your car is properly maintained, with correctly inflated wheels, and no unnecessary weight in the boot, and if you change gear at the right time and avoid excessive acceleration, you can save as much as 10 per cent of your carbon output. But ultimately, in a dirty car that isn't really enough.

And so, farewell old friend...