It's really quite simple. The higher the Reliability Index score, the worse the car is - the lower the score, the better.
As a guideline, the average RI number on the 250 models we compare is 100.The Reliability Index figure is calculated as a combination of:
- the number of times a car fails,
- the cost of repairing it,
- the average amount of time it spends off the road due to repairs
- the average age and mileage of the vehicles we have on our books.
So it's not simply a case of recording how often a car breaks down - it's much more comprehensive than that and the data is constantly updated.
Not all models are present on the Reliability Index - only when we have data for at least 50 vehicles will we display the results - this ensures the integrity of the Index. The small number of omissions this generates will get even smaller with time because the site is linked to claims processed and the number of cars covered is expanding rapidly.
The Index is formed by Manufacturer and also by type/model. This ensures that no individual poorly or highly performing model can unduly influence a manufacturer's overall Index figure.
Another thing to bear in mind when comparing vehicles is that a particular car's reliability score can be dependant on the average age and mileage of those particular cars we hold on file. Normally a newer model will have a lower Reliability Score than a 6 year old vehicle with 70,000 miles on the clock.
Warranty Direct, the company behind the Reliability Index, is able to reveal such valuable information because it pays out millions of pounds a year in car repair bills. The claims Warranty Direct handles provide the data that shows which cars are cheap to run and which are not.
As well as finding out the overall reliability of a car, the Index also offers information on which parts of a car fail most often - air conditioning, axle & suspension, braking system, cooling and heating, electrical components, the engine, fuel system and transmission are all studied. In fact, the only things not included are those 'frictional' and wearing parts that might be replaced at a service such as brake pads, exhausts, tyres, batteries, plugs and pollen filters!
And just to complete the picture, Warranty Direct also collects User Reviews from owners wishing to share their views on their 'pride and joy.' So even if there's one car that breaks down often and costs a small fortune to run, you might just find that its owners still rave about it - The good old Land Rover Discovery might just spring to mind!