What Car? Q&A: July 2009 - Diesel, petrol and jargon-busting

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Diesel or petrol?
Diesel or petrol?
Q) I've been trying to decide whether I would be better off buying a diesel or a petrol version of the new Fiesta. To my amazement, the new 1.6 diesel appears to be more economical than the 1.25 petrol. Is this correct?

Also, I'm confused by some of the jargon, and can't seem to find explanations on the Ford website. What on earth do the terms '90PS' and 'DPF' mean?
Christine Parkinson


A) The 1.6 diesel will do many more miles to the gallon than the 1.25 petrol. Diesel engines are more efficient, so even a less-powerful petrol-powered car could easily use more fuel than a diesel.

However, diesel cars are pricier to buy, so one won't necessarily be the cheaper option for you in the long run.

Taking into consideration all the costs associated with owning both cars, you'll probably have to cover around 66,000 miles in the diesel Fiesta just to break even. If you don't think you'll do that mileage before you sell, then stick with the 1.25 85 petrol.

As for the jargon, 90ps refers to the engine's power. PS stands for Pferdestärke, which is a European measurement for power. We quote brake horsepower (bhp), which is a slightly larger unit. 90PS is roughly 89bhp.

DPF stands for diesel particulate filter. It's a device that removes harmful particulate emissions from an engine's exhaust gases before they are released into the atmosphere. A car fitted with a DPF is more environmentally friendly.

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