ADAC is who responds to essentially every automotive Panne (breakdown) in Germany. And with the Germanic proclivity for thorough record keeping, they have kept them all, and analyzed them more thoroughly than any of Freud’s patients ever were. Did your mother have a flat in 1983? ADAC knows. And they’ve been using it to publish annual best and worst reliability rankings since 1978. If you caught the Toyota Starlet CC, you’ll know that it was the queen of the ADAC numbers, and the bane of Mercedes and the other (once) proud builders of the world’s most presumably durable iron. Since ADAC doesn’t have an easy way to see all thirty year’s worth of the good and naughty, my Germanic side kicked in and I spent a chunk of last night transcribing them unto a spreadsheet, because…well, that’s just how Germanic I am.
A few caveats: The category definitions changed slightly over the years, but they’re close enough. Also, these only show the winners in their respective categories, not an overall ranking. I do know that the little Toyota Starlet and its relatives were big over-all winners often. And to anticipate your concerns, ADAC notes mileage on each vehicle of every call in order to adjust the raw data. And they do the actual response under contract for many of the manufacturer’s mobility program, so they’ve got that covered too. The Germans are very thorough.
I almost left off the most recent decade because there are some questions about whether the numbers are becoming increasingly irrelevant and less reliable due to a number of circumstances. But the number from the eighties and nineties are considered by the automotive manufacturers as very accurate. The reality is that mechanical breakdowns have been dropping pretty steadily the whole time, so that the relative difference between cars is becoming less relevant. Or is that an excuse by the Japanese makes because they don’t show up as often? The German brands are certainly trumpeting their recent improvements. You be the judge.