New cars, bigger problems? Latest Which? reliability data revealed

You’d be forgiven for thinking that newer cars (those aged 0-4 years) typically spend less time off the road being repaired than older ones (5-9 years).

However, it seems there are some uncomfortable truths about car ownership in 2025, and the elephant in the garage is that, according to our data, newer cars spend a fifth more time off the road on average than older ones.

So that new car you’ve paid big bucks for, and expected to depend upon, might actually end up spending more time being repaired than if you’d stuck with your old car or bought an older used model.

Of course, and as you’re about to discover, the devil is in the detail, and if you choose carefully you can increase your chances of buying a reliable car, regardless of its age.

This article was first published in the 2025 Which? Car Guide and includes content exclusive to Which? members.

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Time off road trends

The latest Which? car survey shows that, on average, faulty cars aged 0-4 years spend 4.8 days off the road each year, while those aged 5-9 years are out of action for four days when they need a repair. 

Although that time off the road might be spread across multiple trips to the garage over the year, if your car breaks down on a Monday afternoon, it could be the difference between getting it back for your weekend social activities or having to cancel. And if you commute by car, that’s even more days potentially having to pay for alternative transport to your workplace.

It’s important to state that the data doesn’t say newer cars are more unreliable than older ones. In fact, cars in both age ranges averaged a 7% breakdown rate (where the car could not be driven) in the 12-months prior to our survey.

Plus, older cars were, on average, a little more likely to have at least one fault (driveable or undriveable) in that same time – in our survey, 31% of older cars had a fault compared with 25% of newer vehicles. 

However, while the latest cars are no more unreliable than older models, in some cases dealers and garages are struggling to fix them in good time. Tony Rich, former AA patroller of the year (and current PR manager for the motoring association), surmises this is down to two key factors. 

The first is the supply chain. Tony says: ‘Older, more established vehicles have been around long enough for parts manufacturers to refine their processes and to build a stock of common parts. Parts for newer models are likely to be in the early stages of that process, resulting in delays to the supply chain and the eventual repair.’

The second, and more systemic issue, is a shortage of skilled labour coming up through the industry, given that cars have become so technically complex. Tony called on the industry to ‘help itself’, highlighting that the AA’s own motoring manifesto has called for more training in the industry. 

‘Investing in young people, working with local schools and colleges to offer work placements and other incentives like higher basic pay, subsidised tools and equipment along with structured training programmes’, would all be very beneficial, Tony said. 

Most reliable cars for 2025: see the models that are least likely to let you down

Steer clear of problems

Taking note of our reliability data for the model you’re thinking of buying is key. Beyond that, see if you can negotiate better servicing/breakdown terms from your dealership of choice, and make sure a courtesy car is included.

We’ve found from speaking to owners of faulty cars that they often regretted turning down a courtesy car when the dealer told them their repair would be quick – and ended up taking days or weeks.

Electric reliability

Looking at different types of propulsion, each has completely different common faults. The most frequently seen fault on new EVs relates to onboard computer software (4% of faulty cars aged 0-4 years). 

A big concern prospective EV owners often have about this type of car is that the battery will let them down, but our survey data suggests that this is rarely a big problem. Just 2% of faults reported on new EVs were with the main battery – the same as for 5-9-year-old models.

Charging issues were about the same (2% for newer cars, 3% for older). Compare that to traditional diesel cars, where issues specifically with the fuel system make up 6% of faults on newer cars and 5% on older models – and that’s not including other systems connected to the engine such as the exhaust. 

In short, our data suggests the main means of propulsion isn’t as much of a problem on EVs as it is on a diesel. 

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EV battery degradation

As batteries are used and recharged, they chemically and irreversibly degrade, meaning they can’t store as much charge. However, we’ve found from our survey that, although this does indeed occur, it’s not as drastic as you might expect.

The vast majority (96%) of EV owners with a 2017 or 2018 model told us their battery was still providing more than 80% of its original range (see our news story on EV battery degradation for more). Knowing this, though, it’s worth buying an EV with range that exceeds your needs, in preparation for it dropping in performance further down the line.

EVs also tend to have separate warranties for the battery, usually lasting around eight years. It’s worth checking this before buying as terms (such as the point at which the battery becomes eligible for repair or replacement) vary between brands.

Hybrid heroes?

Full hybrids (those with relatively small batteries that don’t need to be plugged in to charge) are the most reliable type of car, according to our survey. But issues with the 12V battery were more prominent, suggesting that these components are worked harder by this type of engine.

Compared to full hybrids, plug-in hybrids (PHEVs) have larger batteries, which can power the wheels at higher speeds and longer distances before needing to be supplemented by a petrol or diesel engine. However, this appears to come at a cost, with PHEVs being the second-least reliable fuel type for cars aged 0-4 years (diesel being the worst), and the least reliable for those aged 5-9 years. 

Our survey also highlighted one popular car that bucks this trend, but not in a good way. Indeed, this car found a way to go wrong unlike any other. In our survey, 14% of these vehicles had an electric motor problem (a serious, but rare fault among PHEVs), and 12% experienced charging issues.

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