Which? has confirmed that the running costs of diesel cars can often outweigh their economy benefits, particularly after the cars pass three years old. Despite superior fuel economy and usually lower car tax, a Which? investigation has found that new diesel cars are often more expensive to run than petrol cars.
This year is set to be the first in which diesel cars will make up more than half the new car market. However, a Which? comparison of diesel and petrol versions of six popular car models has found that even when the cars are new, petrol engines can be the more cost effective choice for drivers covering a typical annual mileage. Diesel engines may deliver cheaper fuel bills than their petrol counterparts initially but it takes many years before they actually save the average driver1 money.
With drivers having to pay a premium for a diesel car, typically £1000-2000 more on a new car, Which? tests reveal that it could take up to 14 years to recoup the upfront costs in fuel savings. Lower pump prices for petrol and improvements in petrol engine economy mean that petrol cars now often provide better value for money.
The biggest mistake of all is to buy a high mileage three-year-old ex-fleet diesel car on the false assumption that diesel engines are robust enough to take the mileage and continue to offer fuel economy advantages. All too often, dual mass flywheels, diesel particulate filters, EGRs and turbos fail, potentially landing the car buyer with bills greater than the vale of the car.
Which?’s own fuel-economy tests also often fell short of the manufacturers’ claims for both diesel and petrol cars, meaning that motorists shouldn’t place their faith in official miles per gallon (mpg) figures. The Which? study also considered reliability, taking information directly from the 2012 Which? Car Survey, which found that petrol cars are generally more reliable than diesels – both in the first three years of their life (the typical warranty period), and even more so between four and eight years-old.
[Source Honest John]