We should stop buying diesel cars – they aren’t cheaper to run

With news out this week that the UK has the second most expensive diesel prices in the world, we take a look at why you should think twice about that diesel motor...

It’s an undisputable fact that modern diesel vehicles are more economical than petrol cars. Some ultra-efficient oil burners can travel nearly 70 miles on average by burning just one gallon – or 4.55 litres – of fuel.

Example: the BMW 320d EfficientDynamics BluePerformance. It’s a long name, but it can travel a long way on a little fuel, with combined economy of 68.9mpg.

That’s an extreme, however. Take a look at two more normal 3 Series BMWs – it’s a popular car that’s pretty indicative of what a good chunk of UK motorists will drive – and the plethora of external factors at work in the diesel v petrol debate become apparent.

The diesel will set you back a further £2,215

A normal petrol 320i in SE spec will set you back £25,865, the diesel in the same trim will require you to stump up a further £2,215. With fuel economy of 44.8mpg and 61.4mpg combined for the petrol and diesel respectively, there’s no contest on which car is going to take you furthest between fill-ups.

But factor in purchase price and the petrol-powered car begins to haul itself back into contention.

Over a nice round 10,000 miles per annum, the diesel will cost you £1,026 in fuel based on today’s average price of 138.5p per litre, while the 320i will extract £1,353 from your bank account over 12 months with petrol at an average 133.3p per litre.

Factor in the £2,215 price premium of the diesel and you’ll find it’ll take you 6.9 years to recoup the extra cost when new.

You could be chucking £10 notes out the window

Bear in mind that plenty of people change their car every three to five years and it appears you could be chucking £10 notes out the window – now what’s that going to do to your carbon footprint?

The diesel will likely hold its value slightly better come resale time, but the disparity in second-hand values between petrol and the heavy fuel model will have converged dramatically from when they both rolled out of the showroom.

The story is the same across the board. Comparing a 1.4 petrol and diesel Ford Fiesta, with their closer matched purchase prices – £14,900 plays £15,695 – it’d still take you 2.4 years to recover costs.

Do the same test with a Mercedes C-Class and you’ll find that the petrol also only emits 800g more CO2 over 10,000 miles than the diesel.

The headline fuel economy figures that draw punters in aren’t all they’re cracked up to be. Unless you’re going to be doing some serious miles, diesel cars are more expensive to run.

The UK has the world's second most expensive diesel prices

Follow Sean Carson on Twitter @Carson_on_cars

SO WHAT DO YOU THINK? WOULD YOU BUY A DIESEL CAR FOR BETTER DAY-TO-DAY ECONOMY OR A PETROL IF YOU COULD SAVE MONEY OVERALL? TELL US IN THE COMMENTS SECTION BELOW AND JOIN THE DEBATE ON TWITTER WITH #SOCIALVOICES...