How it's measured

Reliability: how its measured
Its not just about how many times a car breaks down, its also about the time needed to fix it and how much it costs to put right. Thats why it pays to arm yourself with the knowledge of how 35 makes and models fared in our 2011 Reliability Survey. Weve used Warranty Directs detailed claims data to analyse what really goes wrong. The survey shows how likely a car is to break down and which areas are most likely to fail.

How is the survey carried out?
Not every make and model of car is included in our survey only the cars that Warranty Direct has policies for, and even then only if there are more than 50 vehicles covered. This large sample size means that we get a more accurate assessment of what really fails. We remove vehicles that are more than eight years old from the results; with vehicles over that age, reliability is more about how well the car has been cared for than its basic design.

What is the Reliability Index?
This is Warranty Directs quick and easy way to compare cars by taking all the key aspects of reliability into account. It factors in the number of times a car breaks down, as well as the average repair cost and repair time. The lower the number, the better the car. As a guide, an average Reliability Index score is around 100.

How are the results shown?
Weve listed the manufacturers from the worst to the best, according to how often their cars break down. However, to help you find the best cars in each category, weve also listed the top 10 and the worst of all sorted by their Reliability Index. This gives a far better comparison when considering the overall reliability of a supermini, compact executive or SUV against its peers. Weve also included the reliability issue thats most likely to cause a problem on each top-10 car.

One thing is clear from this years survey: several manufacturers are consistently failing to deliver an acceptable level of reliability. Were not talking about low-volume, low-rent brands, either. The results start over the page.

The What Car? Reliability Survey is the most robust of its type in the UK, and up-to-date information can be found at any time at Warranty Direct's www.reliabilityindex.com website.