Diesel cars are more than three times as likely to break down as their petrol counterparts and will typically cost 20% more to fix when they go wrong.
Based on analysis of 30,000 faults on three- to eight-year-old petrol and diesel cars over 12 months, car maintenance firm MotorEasy found the average engine repair bill for a diesel was £517, compared with £433 for a petrol model. Diesel cars were sold to many buyers on the basis that they offered better fuel economy, and lower CO2 emissions. However, the VW emissions scandal forced an about-turn and diesels are now very much out of favour.
The study found that Alfa Romeo, Land Rover, Kia and Mazda diesels have the highest average engine repair cost when compared to petrol counterparts.
Diesel engines rely on self-compression, meaning that fuel is compressed to very high pressures, putting more pressure on internal engine parts, it says. Problems can also be more difficult and expensive to diagnose.
Only seven of 25 carmakers analysed showed fewer breakdowns for diesel models – petrol-powered BMWs experienced faults 60% more often, while Audi, Skoda, Mini and Peugeot also bucked the trend. The most reliable diesel cars are made by Skoda, with a failure rate of just 9%, the report says.
Duncan McClure Fisher, founder of MotorEasy, says: “Diesels experience many more small problems than petrol cars. If you’re still considering a used diesel car, our advice is to avoid high-mileage examples, particularly if you are only driving low mileage or doing city driving.”
• The average price of a used petrol car rose by 9.4% during 2017 compared with a 5% fall in used diesel car prices. The comparison website Motorway.co.uk analysed more than 30,000 used diesel and petrol car valuations, up to five years old, generated by online car-buying websites during 2017.
