Older diesel cars are three times more likely to breakdown than petrol models, a study shows.
And there is an extra blow for motorists as diesel cars can cost 20% more to fix when something goes wrong.
An analysis of 30,000 faults on cars three to eight years old found that the average engine repair bill for a diesel model is £517 compared with £433 for a petrol vehicle.
The study – over 12 months – by car maintenance firm Motoreasy also found that engine faults are far more prevalent in diesel than petrol models with the biggest repair bill amounting to an eye-watering £4,030.
The bad news comes as diesel drivers face a new blow with higher taxes for new models from April unless they meet stringent new emissions standards.
Diesel cars are less reliable than petrol for more than seven in 10 manufacturers (71%) with Alfa Romeo experiencing faults four times more than often than petrol models.
The most reliable diesel cars are made by Skoda with a failure rate of just 9%. The higher rate of diesel engine failures is mostly down to the fact that they are under more pressure than petrol counterparts.
Diesel units rely on self-compression, meaning that fuel is compressed to a much greater extent, putting more pressure on internal engine parts.
Least reliable diesel cars
1. Alfa Romeo 47%
2. Land Rover 41%
3. Mitsubishi 36%
4. Saab 33%
5. Mazda 33%
6. Kia 29%
7. Mercedes 27%
8. Vauxhall 26%
9. Mini 26%
10. Audi 26%