About our car reliability survey

• Take care when using reliability data for recent models. Models available for just a few years, such as the Mazda CX-3 (launched in 2016) are likely to top our reliability index. This isn’t surprising – after all, they’re effectively new cars.
• Current reliability doesn’t necessarily indicate how well, or badly, a model will age. Look where older models from the same brand sit in the index. In this case, the older Mazda3 also rides high, which suggests the CX-3 will perform well over the next few years.
• Check out the brand’s overall performance. Mazda again looks good in our brand index. On the flip side, it’s unlikely a brand with a history of below-average performance will suddenly create a reliability superstar (but you never know).
• Not all cars from a more reliable brand will be reliable. Our data show trends and statistically significant results from a sample of almost 10,000 cars. But even among the best-performing brands and models, there’ll always be examples of cars with problems.
  

We wanted to know about reliability problems that happened in the past year. In a change from our 2018 survey, where we categorised the faults, this time we asked respondents to tell us if they thought the fault was serious, major or minor.

• Serious faults are likely to cause a breakdown, take a car out of service for more than a few days and be expensive to repair.
• Major faults could still cause breakdowns or result in significant repair costs and time off the road.
• Minor faults are less critical, but may still need repair or affect owner satisfaction.
• Cars with no serious, major or minor faults were reported as trouble-free.
  

Our reliability index, scored from zero to 100, includes faults reported in our survey – with more weight given to serious faults and less to minor niggles.

To achieve a perfect score of 100, a brand or model would need to have no faults reported. Spoiler alert: no brands or models in our survey scored 100.

Our index allows for age: if a brand or model has better (or worse) reliability than you’d expect for the age of the cars in its sample, our index accounts for it. This means brands and models with older cars aren’t penalised unduly.

We asked owners how satisfied they were with their car and if they’d recommend this make and model to family and friends. Answers were rated on a 0-10 scale; we considered a rating of 8-10 as “very satisfied” or “very likely to recommend”.

We asked about satisfaction with different aspects: fuel economy, comfort, driving performance, safety features, size and practicality, interior styling and equipment and value for money.

We also asked “given your experience with this car, would you still have chosen this make and model at the time you purchased it?”

Finally, we asked owners to tell us how much they’d spent on servicing and repairing their car in the last year. Servicing included regular costs to maintain their car, including WOF fees and replacing wear and tear items such as tyres. Repair costs covered everything else – breakdowns and unplanned repairs.