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How bad is Mercedes reliability, really?

5338 Views 66 Replies 13 Participants Last post by  ccmbduong
I've heard so many horror stories about Mercedes reliability, and CR has of course not been kind.

But how large is the difference between Mercedes and competing vehicles, really?

I suspect that the difference, on average, is less than many people think. There's not much distance between CR's dots--about 0.03 problems per car for a 2006 model--and forums like this one make problems seem much more common than they actually are.

In late 2005 I started conducting my own reliability research. I'm reporting absolute stats like "times in the shop" that will make the differences between cars much clearer. Relative ratings obscure too much--how large is the difference between "better than average" and "worse than average"? I’ll also be updating results four times a year, so there will be information on new models sooner.

I'd like to provide this information on Mercedes models, but so far too few owners have signed up. I have far more owners for competing makes.

To encourage participation, panel members will receive full access to the results free of charge.

Details: Vehicle reliability research

Comments, questions, and suggestions welcome.
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Did you read more than the title?

I'm trying to provide some real information, so people can stop starting so many inconclusive threads on the subject.

Good sig.
I'm sorry for all the confusion.

This is real research. The goal is to be able to say, "The average Mercedes X-Class requires about 1.2 repair trips per year, while the average Competitor Y requires 0.9 repair trips per year. So the Mercedes requires about one extra repair trip every three years." People can then more easily decide if the advantages of the Mercedes outweigh this disadvantage.

Right now, there's no way to make such a clear comparison. As a result, it's very possible that people overestimate how many repairs they'll have with a Mercedes. Everyone is of course aware of CR's take on Mercedes reliability. What few people realize is that the differences between CR's dots for a 2006 model year car is about 0.03 problems per car. That's about one extra problem for every 30 cars.

For the results of my research to be valid, it's as important to know how many cars have not had problems as how many cars have. The problem with gauging reliability from forums is that there's no way to tell how many cars are not having problems. Also, people with problems are much more likely to post here.

To provide the most valid possible results, my research process only collects data on repairs that haven't happened yet (with the exception of the first month). So people sign up, and afterwards report repairs when they happen.

If there are no repairs, participants simply provide an approximate odometer reading at the end of every quarter. That's how I know the total number of cars to include in the analysis.

Currently over 11,000 people have joined, with over 14,000 cars. The problem is that only a few hundred of these are Mercedes.

As stated in the OP, everyone who helps out will get full access to the results for free.
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Credentials: Ph.D. in sociology from University of Chicago, which includes a lot of training in survey research; while there spent five years working at the National Opinion Research Center, a leader in the field.

Your concerns:

Most people who participate consistently participate, whether or not they've had problems.

Unless people check in at the end of the quarter, their responses earlier in the quarter are excluded from the analysis.

When people have gaps in their responses, I follow-up to fill the gaps. This affects only a couple dozen of the couple thousand people who've been responding, about one percent. Only 20-30% of participants report any problems in their first six months of participation.

Your concerns make sense, but the actual data demonstrate that they aren't actually problems.


Not much right now. Eventually there will be two ways to gain access to the results: participate in the research or pay a membership fee. Right now only the first is available. I feel this is a very fair way to structure the research, since those who want others to do all the work will enable those who do the work to get the results for free. With CR, you pay just as much even if you take the time to fill out their surveys.
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Just enter 99 for the license plate. This is what most people do, usually because they can't remember the number.

I ask for the license plate because some people are very suspicious of others and suggested that I need a way to verify that cars actually exist.

If responses for a model ever seem suspicious I reserve the right to request the plate number so I can verify that a car exists. But I have not had to do this yet, and it's not likely to happen in the future.

I ask for the license plate and not the VIN because few people are going to take the time to look up their VIN, and it's much easier to remember a plate than a VIN.
Your choice whether or not to participate.

As I'm sure your recognize, every car is equally important, since the goal is to have a representative sample.

There are certainly challenges to survey research. But I've designed this research to overcome these challenges as much as possible. My sample sizes are currently small, yet the results have a great deal of face validity (i.e. they make sense).

Most recent results:

TrueDelta Vehicle Reliability Survey results

Next update will be mid-week.

I doubt it'll make much money. Hoping it'll eventually make enough to get my wife off my back. She's not crazy about the current income/time spent ratio. I believe that if I focus on providing the best possible information, the rest will take care of itself.
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I only collect data going forward anyway. The past doesn't necessarily predict the future. One of the things I hope to determine is the strength of the link between the two.

The main point of the research is a focus on absolute repair rates. I think many people will be surprised that even models with relatively poor reliability aren't in the shop all that often. Putting everything in terms of red and black dots can (and does) obscure this fact.

The fact of the matter is, with CR if more than 1/4 of owners of a 2006 or newer car report a problem, the model gets a big black dot. How many readers then assume that they're guaranteed to have many problems if they buy a car with a big black dot?
There's hardly any work involved if your car never requires a repair. Just four approximate odometer readings a year, takes about two minutes.

I think most people will have a repair trip or two a year, so about ten minutes.

In response to the other guy, the method I'm using won't yield perfect information, but it will yield much better information than car buyers have access to today.

Mercedes owners are clearly must less interested in the research than most. So it looks like people who want reliability information on Mercedes will have to continue to rely on CR for the time being.

My apologies. I forgot to consider that Mercedes owners are far more intelligent than people who buy other cars.

Actually, I suspect that the problem is that people who care about reliability information read CR, and as a result don't buy Mercedes. So there aren't many Mercedes owners who care about reliability information.

Just do me a favor and don't slur the research unless you've looked into the details of what I'm doing. Which I strongly suspect you have not.

For everyone else, it's a simple decision. If you feel no need for reliability information or feel that CR does a good enough job, then don't help out. If, on the other hand, you want to help provide a superior alternative to CR, this is the way to do it.
I'm making no judgments on the quality of Mercedes automobiles. The title was a take on the CR-fed press stories. I see my research as a corrective, not more of the same. I feel my earlier posts in this thread make this clear.

You sure are quick to use the harshest terms to describe what I'm doing without any support. Sorry, but words like "bullshit" are no substitute for a well-reasoned argument.
Where do you guys get this stuff?

I'm not pro or anti any brand and I get money from no manufacturer.

I should add that I also don't think CR or JD Power or anyone else intentionally tilts their research results for or against any particular brand. We use different methods, and I think mine are better, but we're all reporting responses from owners.

Then again, I also think the moon landing actually happened.
Can everyone dial it back a few notches?

I do suppose the title was to get people's attention, but it is a question I'd like to answer, without bias. I don't already have the answer, or there'd be no point in conducting the research.

German cars in general don't have the best rep for reliability. But owners have been reporting relatively low repair rates for the 2006 BMW 3-Series and the 2005.5-2006 Jetta, and that's what my site is reporting. (The 2006 Passat hasn't been faring so well.)

Was I personally a bit suprised by these results? Absolutely. But this had no bearing on the results. They are what they are.
The survey is pretty straightforward. Either the car went into the shop and something was fixed, or it didn't.

Unlike CR, I don't have individual respondents decide which problems are serious enough to report, which admits all sorts of biases. Everything beyond routine maintenance and an explicit list of wear items gets reported.

This is not your typical online survey. Those are thoroughly unscientific. Mine would be as well if I were collecting repair histories. But I collect repairs going forward. When people sign up, they do not know what they'll be reporting in advance. This is a key difference.

With both CR and JD Power, people know what they're going to say when they decide whether or not to participate. This could lead to non-response bias.
asianml said:
If you read his previous posts, the research data he is asking for is coming from present problems (or lack of) and future problems (or problem free). The past is not a part of the research.
Exactly. Though I wish I didn't have to collect data on present problems at all, as this could admit some bias. Problem is, it would then be much more difficult to get data on the first month or so of ownership.

Luckily, over time the percentage of data coming from people who have just signed up will be smaller and smaller.
Routine maintenance and wear items don't get reported.

From the survey form:

Problems with these never count as problems:
Light bulbs -- if not a headlight and takes less than 5 minutes to change
Suspension alignment
Clutch lining
Fluids (oil, coolant, etc.)
Spark plugs and wires
Wiper blades
Belts, including timing belt
Radiator hoses

I also exclude brake pads and rotors from the main analysis. I didn't used to collect data on them at all, but many people wanted me to. So I've started asking people to report brake jobs, but will be reporting any results for them separately.
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A few reasons:

1. It would require far more work from participants, and it's hard enough to get people to put in the time currently required

2. Few people are going to admit to not doing the required maintenance. They'd either claim to have done it or, more likely, just not participate

3. People who take part in the research are interested in reliability and are responsible enough to consistently respond to the surveys. Responsible people interested in reliability likely do at least the required maintenance.

4. Most things that break are not things that can be maintained: power window motors, audio systems, alternators, and so forth. And of the items subject to maintenance, only some will be caused by lack of maintenance. Ultimately, a very small percentage of repairs will be due to insufficient maintenance.

5. If need be, I can follow up in cases of major failures to find out if they might have been caused by insufficient maintenance. I don't have plans to do this, but it's a possibility, and would be a much more efficient use of people's time than having everyone report all their maintenance. #2 will still apply, but it will apply regardless.
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Another marketing rep? There is no marketing rep. There's only me. Welcome to the power of the Internet.

Collecting maintenance information wouldn't be too much work for me. It'd be too much work for participants. In other words, far fewer people would participate. And it's hard enough to get people to participate as is.

There are many more things I'd ask if it would not have an impact on participation to ask more questions.

But it would. So it's necessary to figure which questions are most necessary to ask, both in terms of the likely quality of responses and the usefulness of responses.

You're dealing in hypotheticals, and unlikely ones at that. I've been up close and personal with actual data for six quarters now. I read every response. Every three months I tweak the survey based on what I've learned. The actual data have not indicated a need for maintenance information.

It's possible that CR and JD Power do not collect maintenance information for the same reason.

Are the results of this research perfect? Of course not, very little is. But they will be much better than any reliability information currently available.

Wait for something that's perfect, and you'll never have anything.
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Thanks for the info and links.

J.D. Power does a different sort of survey in the UK. It's measuring overall satisfaction, and the reliability component asks for owners' opinions about the reliability of their cars. Good info to have, but not the same as measuring repair rates.

My own research strives to highlight the size of differences. Often these aren't large. I encourage the same approach with this J.D. Power survey. Most of the brands' scores are within a few points of the average of 79.

If one brand has a satisfaction score of 76, and another has a satisfaction score of 82, is that six-point difference really worth paying attention to? This range includes all brands from #6 Jaguar to #29 Peugeot.

Similarly, every brand from #10 Volvo to #25 Mitsubishi falls within two points of the average.

Looked at another way, how different are VWs, Skodas, and Seats? Since I'm in the U.S., I must admit I don't know the answer to this question, other than that they are based off the same platforms and tend to closely resemble one another. Yet Skoda's CSI score is 84.5, VW's is 80.2, and SEAT's is 77.8. Quite a range in the context of this study.
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MarcusF said:
As an example, there’s a service recall for the W208 voltage regulator. Low voltage will fry a PW motor. A bad voltage regulator can cause the alternator to overheat and fail. Voltage spikes can kill any audio system. Without bringing a car in for "service", how does one get a "service recall"?
What are the details behind this recall? Is this a full recall, where owners are being mailed and Mercedes is replacing the voltage regulator free of charge no matter how many miles are on the car?

FWIW, my surveys would note if this had been performed. Recalls are recorded, though they aren't counted as repairs in the analysis because I wouldn't want to give manufacturers further reason to resist them.
Owners are asked whether they learned of the problem being repaired through a recall or TSB. This is one of the questions on the survey.

Owners are not legally required to use Merecedes dealers for service. As you describe the service recall, it is only performed if someone happens to bring their car to a Merecedes dealer for service.

Since it is not a true recall, I would consider the repair itself or any problems that result from not having the repair performed as repair trips in my analysis.

If Mercedes wants this repair performed on all affected cars, owners should be directly notified.
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