The most unreliable used cars in the UK

What are the most unreliable used cars in the UK?

By Warrantywise's 2026 Reliability Index, the Land Rover Discovery scores lowest, followed by the BMW 7 Series, Mercedes-Benz S-Class and Audi A7. The index scores each model out of 100 from repair requests made on Warrantywise's used car warranties between January 2023 and January 2026, for cars aged 3 to 15 years. A lower score means a higher repair risk.

Source: Warrantywise Used Vehicle Reliability Index 2026, published 27 March 2026 and checked on 26 October 2026. The S-Class and A7 tie on 19.2; Warrantywise puts the S-Class higher because its average repair cost was higher. The index gives one score per model, not per generation, engine or year, so it can't say which versions of a model drove its score.

How does the Warrantywise Reliability Index work?

It scores models from Warrantywise's own repair data, not from owner surveys or carmakers' claims. The 2026 index draws on around 1.6 million data points, and a model needs at least 250 cars on a Warrantywise plan to be scored. Four measures make up the score: how often repairs were requested, how long they took in labour, and the car's age and mileage at the time. Warrantywise doesn't publish how it weights them.

That makes it a measure of warranty repairs on cars whose owners bought a Warrantywise plan. Warrantywise sells those plans. It doesn't see faults fixed outside its warranties, and a model with fewer than 250 cars on its plans isn't scored.

Is a reliability index the same as an owner survey?

No: an index like Warrantywise's counts repair requests, while an owner survey such as Which?'s asks drivers what went wrong. They measure different things, so the same model can rank differently in each.

Which? publishes its own ratings on its site, so we don't repeat them here.

What do the lowest-scoring used cars have in common?

All 10 are premium cars, Warrantywise says, and seven of them are SUVs. In its May 2026 write-up of the bottom 10, it put their average repair cost at £2,051.63, and said their repairs typically came at six to seven years old and just under 70,000 miles.

• •Emissions-related repairs were the most common type, in four of the 10 models: sensor faults, exhaust problems, and EGR valve and diesel particulate filter (DPF) trouble.
• •Electrical and suspension faults also came up often across the 10.
• •Warrantywise puts the low scores down to complex electronics, the extra strain that big cars put on suspension, drivetrains and brakes, and long-term use, more than to how the cars were built.

Does a low score mean the car I'm looking at is unreliable?

No: a score describes repair requests across many cars of a model, not the one in front of you. Warrantywise itself says its index shows trends, not guarantees, that not every car from a maker will have problems, and that a well-maintained car may have far fewer. A high score doesn't mean no risk either: any car can need a repair.

How a car was serviced, driven and used also plays a big part, Warrantywise says. So a car from a low-scoring model with a full service history and a clean MOT record can be a safer buy than a neglected one from a high-scoring model.

How do I check a used car's reliability before I buy?

Use the model's score as a starting point, then check the history of the car itself.

1. 1

   Look up the model

   If it's in the bottom 10 above, budget for repairs, especially on a car around six or seven years old, when Warrantywise says repairs on these models typically came.

2. 2

   Read the MOT history

   Advisories that come back on the same part year after year, such as suspension, brakes or emissions, show what's wearing out.

3. 3

   Check the mileage adds up

   Each MOT's mileage reading should be at least as high as the one before it.

4. 4

   Ask for the service history

   Look for services on time, with stamps or invoices whose mileage fits the MOT readings.

5. 5

   Get an inspection

   For a premium SUV or saloon, have an independent mechanic look it over before you pay.

CarCanny's full report shows every MOT test with its mileage and the tester's advisories, and checks whether the mileage ever went down between MOT tests. It also checks finance, write-off and stolen. The free check shows the car's details from its DVLA record, so you can match them against its logbook.

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Written by

Hubert Rachwalski

Founder and car enthusiast at CarCanny

Hubert is the founder of CarCanny and a car enthusiast. He built CarCanny as the check he wanted as a buyer: simple, clear and honest about what it does and doesn't know.