British-based insurance company Warranty Direct has been insuring cars against breakdowns since 1997 - more than 200 000 of them so far, spread across 450 individual models.
It has also kept accurate records - model by model - of which ones broke down most often in relation to age and distance covered, how much the breakdowns cost and how long the cars were off the road.
Now, to celebrate 15 years in the business, the company has compiled its top 10 lists of the most reliable - and least reliable! - cars in the UK between 1997 and 2012.
The Warranty Direct Reliability Index is calculated on a inverse scale: the lower the Reliability Index, the more reliable the car.
COMPLEX FORMULA
It's worked out according to a complex formula that takes into account the cost of individual repairs as well as the frequency of failures, especially on luxury models, which may not break down as often as entry-level cheapies, but cost an arm and a leg to fix when they do.
That's why the Porsche 911 gets a bad rating even though its failure rate is only 39 percent - the best in its class. The average cost of Porsche 911 breakdowns over a period of 15 years was a jaw-dropping £847.52 (R12 000)
The same can be said of Mercedes-Benz, according to the records, with three models in the bottom 10 of the reliability rankings. For instance, the SL breaks down less often than any other car in the “10 worst” group, but high repair costs give it a poor rating.
This is not uncommon: expensive cars have a lot of complex features. Not only is there more to go wrong but when it does it's very expensive to fix.
THE TOP 10
At the other end of the scale, seven of the 10 most reliable cars in the UK carry Japanese badges - One Mitsubishi, two Toyotas, two Hondas, a Mazda and a Suzuki.
The Mitsubishi Lancer came out with the best Reliability Index, followed by the Vauxhall Agila - a built-in-England version of the Suzuki Wagon R+ that uses Opel engines.
Mazda, in fact, very nearly made the top 10 twice with the same car: the third-generation MX-5 roadster rated seventh, while its predecessor just missed the cut, coming in at 11th overall.
THE MOST RELIABLE CARS:
1 Mitsubishi Lancer (2005-2008) Reliability Index = 6.
2 Vauxhall Agila (2000-2008) 8.
3 Suzuki Alto (1997-2006) 9.
4 Toyota Aygo (2005-2012) 10.
5 Honda HR-V (1998-2006) 16.
6 Volvo S40 (1996-2004) 16.
7 Mazda MX-5 (2005-2012) 19.
8 Mercedes-Benz E-Class (2006-2012) 20.
9 Toyota Yaris (1999-2003) 20.
10 Honda Jazz (2001-2008) 21.
THE MOST UNRELIABLE CARS:
10 Citroen XM (1994-2000) 438.
9 Land Rover Range Rover (2002-2012) 440.
8 Porsche 911 (2001-2006) 442.
7 Bentley Continental GT (2003-2012) 490.
6 Audi A6 Allroad (2000-2005) 502.
5 Mercedes-Benz CL-Class (2000-2007) 512.
4 Mercedes-Benz V-Class vans (1996-2004) 547.
3 Mercedes-Benz SL-Class (2002-2012) 555.
2 BMW M5 (2004-2011) 717.
1 Audi RS6 (2002-2011) 1282.