18 Aug 08
The problem is that diesel cars emit more carbon dioxide per litre of fuel burnt.
In our real-world fuel economy investigation CO2 emissions for the Toyota Aygo (petrol) and Skoda Fabia Greenline (diesel) are both officially rated at 109g/km, but the Skoda's official economy is 68.9mpg against the Toyota's 61.4mpg. In other words, diesels have to work much harder at being frugal to achieve the same carbon dioxide figure as a petrol car.
Point taken, you say, but the Skoda still uses less fuel, even in the real-world test, and that's got to be good for a family's budget, right? Well yes, but only up to a point.
An expensive choice?
So feted are small diesels right now that they're becoming prohibitively expensive to buy second-hand. The typical £1,000 extra you have to pay over a petrol when new is being carried over into the used market.
'Traditionally diesels struggle at the smaller end of the market, but right now the situation is completely reversed,' says Jeff Paterson, chief car editor of used-car bible Glass's Guide. 'The lower VED encourages people to go for them and now we're seeing premiums for the small diesels massively increase over petrol - up to £1,000 for two-year-old 1.4 diesels.'
That leap in price then has to be factored against the diesel savings. Small diesels generally fall into the £35 annual tax bracket, against £120 for the typical small petrol, which yields a pretty healthy saving of £85 a year. Not bad, but that's a still few years before the grand is clawed back.
