According to research from Which?, the reputation diesel cars have for saving motorists money has faltered over the years and improved technology. The consumer group found that most diesel vehicles are actually more expensive than petrol cars. Although diesel engines can deliver more miles per gallon, they can also take up to 14 years before saving money for the average driver. This is due to the higher cost of the vehicles and the diesel fuel they use, which can be nearly 6p per litre more than unleaded petrol.
Which? says that, with motorists paying a premium for diesel cars – usually around £1,000-£2,000 more for new vehicles – their tests show that it could take as long as 14 years before the owner recovers the upfront costs by saving on fuel. Lower petrol prices at the pump and advances in petrol-engine efficiency have meant that petrol vehicles frequently offer better value for money. This comes as diesel vehicles make up over half of the new car market.
Which? compared the different petrol and diesel versions of six vehicles: Vauxhall Astra, VW Sharan, Peugeot 308 SW, Volkswagen Tiguan, Ford Fiesta and BMW 5 Series. Calculating the annual fuel bill for each vehicle based on an average of 10,672 miles, it found that the petrol engine was the better option for four out of six of the cars for a motorist travelling 10,000 miles a year. The group noted that drivers doing fewer miles than this will almost always find petrol is the best choice.
In more detail, Which? found that it would take an automatic, diesel version of the BMW 530d SE over 14 years to be as cost effective as the petrol version of the BMW 528i SE Step Auto. The 530d SE costs £40,945 and gets 40.9mph, while the 528i SE Step Auto costs £37,300 and gets 34mph. The 1.6-litre diesel Ford Fiesta TDCi, which costs £15,495 and averages 62.8mpg, would take 7.8 years to save the owner as much as they would save with the 1.25-litre petrol version, which costs £13,095 and averages 47.1mpg.
However, it would only take three years for a driver to recoup the cost of a diesel VW Sharan 2.0 TDI, which costs £27,800 and gets 47.9mpg. This is the common replacement cycle for many drivers. Its equivalent is the 1.4 TSI petrol version, which costs £26,475 and averages 35.3mpg. Additionally, it will take just 3.1 years for the Peugeot 308 SW 1.6 3-HDi diesel estate (£18,665 and 60.1mpg) to overtake the 1.6Vti petrol version (£16,895 and 38.7mpg).
Which? says that, although company car drivers who travel a lot of miles may find the BMW diesel option better, private consumers should buy petrol. This is because the premium for diesel version means owners will nearly never recover the extra cost in terms of fuel savings. The report says the disadvantage is that the diesel Fiesta will have to be kept for a long time before it recoups the premium in fuel savings. Motorists who do most of their driving around town will recoup the cost in about four-and-a-half years, but this will take closer to eight years for motorists doing a mix of driving.
Which? added that diesel vehicles have become more refined than in previous years, but it’s getting tougher to justify the premium purchase price with petrol about 5.5p a litre cheaper than diesel and some manufacturers offering more efficient petrol engines. Drivers have moved on from the ‘days of clattery diesels’ and from diesels being the preferred option of cars for economical motoring.
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