Revealed: the cars with unacceptably high fault rates
Our unique reliability data shows you can't necessarily rely on cars from premium brands being more dependable.
Every year, we ask thousands of UK car owners about their experiences with their car, including any faults they’ve had in the past 12 months.
In our latest survey*, we heard from 50,323 drivers about the 59,921 cars they owned. Using this data, we've identified several cars with above-average instances of specific faults.
And while some faults are more serious than others, the eight cars we've selected were affected by certain faults far more than other models of similar ages, yet the vast majority of owners who reported these faults also told us that the fault wasn't fixed through a manufacturer recall.
Looking for a car that won't let you down? See our guide to the most reliable cars for 2024
Alpine A110 (2018-)
| Fault (age range) | Alpine A110 fault rate | Average fault rate for cars in this age range |
| Fuel system components (0-4yrs) | 35% | 4% |
| Exhaust/emission components (0-4yrs) | 16% | 3% |
| Cooling system components (0-4yrs) | 16% | 3% |
Currently Alpine’s only model, the A110 sports car is blighted by several faults, according to our latest survey. More than one in three owners reported serious fuel system component faults. Owners told us their cars broke down, failed to start or reported that the car was unsafe to drive. Even more concerning is that this fault affected seven times more cars than is typical for cars aged 0-4 years.
Slightly less serious cooling system component faults were also reported, with broken down cars and vehicles that were unsafe to drive occurring in half of all cases of this fault. The exhaust and emission component faults were relatively minor, though: a quarter of instances of this fault left the car drivable but unsafe, according to owners.
Read our full Alpine A110 (2018-) review.
Alpine's response
‘All Renault Group brands are committed to customer satisfaction as a top priority. As a part of its quality policy, Renault Group deploys Recall or Service Campaigns as often as necessary to ensure customers complete peace of mind with their vehicle.
‘In regards to fuel system faults, we confirm that a service campaign was implemented in December 2023, with more than 50% of cars now rectified. Anyone seeking assistance should contact their local Alpine Centre.’
Audi A1 (2010-18)
| Fault (age range) | Audi A1 fault rate | Average fault rate for cars in this age range |
| Fuel system components (5-9yrs) | 18% | 4% |
Nearly one in five owners of petrol first-generation Audi A1s in this age group told us their car suffered from serious fuel system component faults.
A quarter of the reported faults left owners without a car to drive, while around 40% of owners reported a breakdown as a result of this issue.
Read our full Audi A1 (2010-18) review.
Audi A3 (2012-20)
| Fault (age range) | Average fault rate for cars in this age range | Average fault rate for cars in this age range |
| Fuel system components (5-9yrs) | 18% | 4% |
| Fuel system components (5-9yrs) | 18% | 5% |
The previous generation of the Audi A3 Sportback suffers from serious fuel system component faults. More than three in five cars aged 0-4 with this issue were left undriveable because of the fault, and 39% of cars with this fault broke down.
The picture looks better for older diesel models, though, with 35% of owners reporting that their cars were still able to be driven safely with the fault. A slightly higher percentage of cars were reported unsafe to drive, though.
Read our full Audi A3 (2012-20) review.
Audi A3 Saloon (2020-)
| Fault (age range) | Audi A3 Saloon | Average fault rate for cars in this age range |
| Fuel system components (0-4yrs) | 25% | 4% |
A quarter of owners we heard from told us their car was affected by this issue. Half of owners who experienced this fault reported that their car wasn’t safe to drive, while others couldn’t be started or broke down as a result of this fault.
Audi declined to comment when contacted.
Read our full Audi A3 Saloon (2020-) review.
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BMW 1 Series (2019-)
| Fault (age range) | BMW 1 Series | Average fault rate for cars in this age range |
| Exhaust/emission control system components (0-4yrs, diesel only) | 16% | 5% |
According to our survey, several BMWs are affected by faults related to exhaust or emission control components, including newer versions of the diesel BMW 1 Series. This fault affected more than three times as many cars than we’d expect from diesels of this age.
A third of owners who experienced this fault reported their car as being unsafe to drive.
Read our full BMW 1 Series (2019-) review.
BMW 5 Series Saloon (2017-23)
| Fault (age range) | BMW 5 Series Saloon | Average fault rate for cars in this age range |
| Exhaust/emission control system components (5-9yrs) | 16% | 5% |
Older versions of the previous-generation 5 Series Saloon have a relatively high number of faults with exhaust and emission control components, according to our survey. However, over half of cars were reported as still be drivable, despite suffering from this fault.
Read our full BMW 5 Series (2017-23) review.
BMW's response
‘The BMW Group UK has a long-term commitment to quality and quality control. Without further details relating to your statement regarding the three models in question, we are unfortunately unable to give a specific comment.’
Mercedes-Benz C Class Estate (2014-21)
| Fault (age range) | Mercedes-Benz C Class Estate | Average fault rate for cars in this age range |
| Exhaust/emission control system components (5-9yrs, diesel only) | 17% | 5% |
Early versions of the previous-generation C Class Estate are another premium car to suffer from relatively high instances of exhaust component faults, although most cars with this issue (85%) were reported as still being safe to drive.
Read our full Mercedes-Benz C Class Estate (2014-21) review.
Mercedes-Benz's response
‘At Mercedes-Benz, we continuously monitor the performance of our cars and pay particular attention to any issues that could have an impact on reliability and customer satisfaction.
‘We are unable to comment further on this generalised topic and the results of your survey without reviewing specific cases, the associated individual circumstances and the root cause of any reported malfunctions.’
Volkswagen Tiguan (2008-16)
| Fault (age range) | Volkswagen Tiguan | Average fault rate for cars in this age range |
| Suspension components (5-9yrs) | 22% | 4% |
| Suspension springs (5-9yrs) | 13% | 3% |
Our survey shows that the first-generation Volkswagen Tiguan suffers from unusually high instances of suspension component and spring faults, all of which affected far more owners than we’d expect in cars of this age.
With the spring fault, the vast majority of owners told us that the fault resulted in their car being unsafe to drive. This figure was 50% for the suspension component fault.
Volkswagen did not respond in time to our requests for comment.
Read our full Volkswagen Tiguan (2008-16) review.
Discover the most (and least) reliable car brands for 2024
What are your rights if you have a faulty car?
If a new or second-hand car you bought develops a fault, you could get it repaired or replaced at no further cost to you by whoever sold it to you. Alternatively, you might be able to get your money back.
Depending on how you bought your car and who from, we can explain your rights. Use our free tool.
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The 2024 Which? car survey is now open. This is your opportunity to tell us about your experiences with your car – the faults you've encountered, what you love and hate about it and more.
Your feedback helps shape our car reviews and lets us push manufacturers to fix faulty cars.
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Take part in the 2024 Which? car survey today.
*Data based on the latest Which? car survey, in field May 2023 to July 2023
