Petrol versus Diesel Cars: Which is Cheaper to Run?

Written by Karen Bryan

We’ve been looking into buying a replacement for our 7 year old Skoda Fabia 1.4TD. I bought the car pre-registered with 6 miles on the clock in 2004. At that time I was doing around 20,000 miles a year so having a diesel car was a no- brainer. However our annual mileage has significantly dropped to around 8,000 miles since I gave up my day job.

The price differential  between a new petrol and diesel supermini seems to be between £1,500 to £2,000. Most people say that you need to drive at least 14,000 miles a year to make buying a diesel car worthwhile. It also depends on the difference in the real (versus official) average miles per gallon between a petrol and diesel version of the same car.

We did some rough calculations of the difference in fuel costs between the petrol and diesel versions of a couple of Vauxhall cars based on an annual mileage of 10,000 miles and official consumption figures. A Corsa 1.2 petrol would cost £160 more a year in fuel than a Corsa 1.3 diesel. An Astra 1.6 petrol would cost £200 more on fuel per year than an Astra 1.9 diesel.

Therefore if you kept your car for 8 – 10 years you could probably recoup the difference between the purchase price of a diesel versus petrol car through fuel savings, even if you only drive 10,000 miles a year.

We also observed that UK road tax was cheaper for some of the diesel models and a difference in price of £50 a year in road tax equates to a saving of between £400 – £500 over 7 – 10 years of ownership, assuming the differential remains constant.