It's pretty much common knowledge that Mercedes-Benz spent a few years in the woods with respect to quality/dependability issues several years back, mostly in the late 90s/early 00s, depending on model. Many of the issues had to do with electronics/sensors/control systems etc, and Mercedes took a (well-deserved) beating in the motor press and even in the popular consciousness.
Now, obviously JDP
is just one set of data points, and I don't place too much value on its IQS (Initial Quality Survey) which seems to get the most mention in the mass media. However, I think its VDS (Vehicle Dependability Survey) is more meaningful, in that it tracks reported issues over the first three years of the car's life.
The charts below show these reports, and remember each chart refers to the models of three years previous
. That is, the 2014 survey pertains to 2011 cars. Certain year-over-year anomalies come about because a new model was introduced which had teething pains, and drags the entire make/nameplate down. Jaguar's XF was a case in point. Ford had worked wonders with Jaguar's notorious reliability rep but the introduction of the XF in 2008-09 clobbered Jaguar's rating (see 2011/12 in comparison with previous years).
Look how poorly MB's 2002 models fared in the first survey from 2005, then note the trend:
Daimler's dramatic improvement over this period is no small feat, since nearly every other mfr was trying its best to improve as well. Never before in history have so many cars been so durable and dependable. Note that the industry average dramatically improved over the period shown here, though it crept up slightly in the past few years, possibly due to the increased complexity of electronic driver aids. Finally, it's worth noting that among the limitations in the JDP surveys is the fact that all reported issues are treated equally; that is, a Bluetooth pairing fault counts as much as a transmission failure.