2021 What Car? Reliability Survey

The UK's used car market is booming, with demand frequently outstripping supply, and that’s sending prices of the most popular models up by as much as a third. This unique set of conditions means that more of us than ever are looking for guidance on the best second-hand cars to buy.

A crucial factor in choosing the best used car is reliability. If you buy a good one, you’re unlikely to have to pay out for anything other than consumables and servicing as it ages. Pick one that suffers a stream of costly faults, though, and the bills will soon start to rack up.

That’s where the annual What Car? Reliability Survey can help. We’ve asked more than 16,000 car owners to tell us if their car has suffered any problems over the previous year, and if so, in which areas.

The 15 categories of fault are air conditioning, battery, bodywork, brakes, clutch and gearbox, engine, engine electrics, exhaust, fuel system, infotainment and sat-nav, interior trim, non-engine electrics, steering, suspension and 'other'.

To get an indication of how serious each fault was, we also asked owners to tell us how long the car was out of action for and how much the repairs cost. The worst offenders were off the road for more than a week and cost more than £1500 to fix, while those with minor niggles were usually put right in a day or less and were often fixed for free.

Those two factors are more important than what actually went wrong, so we used a combination of them to calculate a unique reliability rating for each model we’re told about.

The 2021 What Car? Reliability Survey contains data about 178 models aged up to five years old, from 30 brands.

Most reliable small cars 

1. Dacia Sandero (2013-2020)

Reliability rating 100%

What went wrong? Nothing

The latest Sandero is the UK’s cheapest car to buy new and the previous version is one of the most dependable of those up to five years old. Not one of the cars that readers told us about have suffered a single fault, and two-thirds of Sandero owners said overall reliability was the best thing about their cars.

Owner’s view “My family has had three Sanderos; the oldest is seven years old and has provided faultless service”

2. Hyundai i10 (2014-2020)

Reliability rating 99.6%

Only 4% of i10 owners told us their cars had gone wrong, and even though some of the cars were out of warranty, the dealers resolved all issues without a fee. The only problem area highlighted was the steering, and all faults were put right in a day or less.

3. Suzuki Swift (2017-present)

Reliability rating 99.3%

Just 3% of Swifts suffered a fault in the previous 12 months, according to owners, with air conditioning glitches the only issue. All cars could still be driven, and all repairs were carried out for free, but all the vehicles involved spent more than a week in the service department.

Least reliable value and small cars 

1. Ford Fiesta (2017-present)

Reliability rating 74.9%

What went wrong? Suspension 18%, battery 15%, engine 15%, steering 15%, exhaust 12%, interior trim 8%, sat-nav 7%, bodywork 6%, engine electrics 6%, non-engine electrics 6%

Owners highlighted serious issues, with common problem areas including the engine and suspension. Overall, 34% of Fiestas went wrong, with 40% of these taking more than a week to put right. The only good news is that 100% of the repairs necessary were done for free.

Owner's view "My car’s problems started when it was just three weeks old, and have included water leaks, suspension issues and broken engine mounts”

2. Volkswagen Polo (2018-present)

Reliability rating 80.6%

Although 47% of Polos had a problem, more than two-thirds could still be driven and 21% were back on the road in a day or less. Owners told us that 91% of work was done under warranty, but a minority paid out between £750 and £1000. Problem areas included the engine and its electrics, plus air-con and interior trim.

3. Seat Ibiza (2017-present)

Reliability rating 90.5%

Owners told us 29% of Ibizas went wrong. The most common complaints were minor niggles with the bodywork, but there were also reports of problems with the air-con, engine, gearbox/clutch and non-engine electrics. Seat took care of the cost of all repairs, though, and only 13% of cars took more than a week to fix.

Reliability of small cars aged up to five years old

Next: Most and least reliable family cars >>

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