I've definitely thought of this, which is why two of the survey questions from the start has asked whether or not the car had to be towed and whether or not it could have been driven dependably for another week.

The thing is, both are rare. Only about one problem in 20 requires a tow, and only about one in eight renders the car undriveable. And this is for cars of all ages--they're even more rare for fairly new cars. Which people probably don't realize, so this would be good information to get out there.

The more rare something is, the larger the sample size you need to accurately measure it. Even to do the latter I'd like to have a minimum sample size of 250. We're simply not there yet.

People who buy brands known for reliability do tend to be more interested in reliability surveys. But the major factor is how many of a model are sold. In the first seven months of this year Mercedes sold 10,596 of the GL, while Acura sold 24,724 of the MDX.

This may be a dumb thought, but why can't we have both? Good handling, ride dynamics, reliability and design all in one? Is that unattainable?

I wish it were possible. My solution has been to always own at least one Japanese vehicle. I love German cars but just haven't found them to be too reliable. Maybe the Germans push the envelope a little more too. You don't have to worry about the turbo going out on a Landcruiser because they don't make a diesel (at least not for sale in the US). You don't have to worry about the air suspension failing on an Infiniti QX (maybe not the best example of reliability) because it doesn't have air suspension. I could go on.

It is unfortunate that your sample size is not larger because while the overall repair trips/year per 100 cars is informative and important to me, what I care most about is if I can put my wife and 3 kids in my GL and be able to make it to my destination and back without interruption.

I'm trying to decide if I should buy an extended warranty right now and part of my diliemma is that I have to ask myself if saving the few thousand dollars by not replacing my GL every 4 years is worth the potential interruption to our family vacation from a car breakdown. Honestly, saving a few thousand dollars by keeping my GL two additional years isn't worth being stranded in Western Michigan for a day while my GL gets worked on.

The odds of getting stranded on vacation should be very low.

Some rough calculations with conservative assumptions...

You're on vacation for perhaps two weeks a year, and perhaps 15% of the total miles driven for the year? The odds of a problem that must be fixed right away at any point in the year are perhaps one in four for an out-of-warranty GL. So the odds of a breakdown on vacation might be one in 25 each year.

Spend even $1,000 to avoid that one in 25 breakdown, and you're essentially paying $25,000 per on-vacation breakdown.

Now, I haven't factored in Murphy's law...

I'm not sure I follow the whole $25,000 per on vacation breakdown figure (I hated statistics in college) but I get your point that breakdowns causing trip interruption are rare. When you look at some of the stats on your website, they are a little scary. I guess it is good to have this context.

But they do have a turbodiesel that doesn't break down, and they do have air suspension (at least on the Lexus) that doesn't break down, and they do have advanced electronics that are (generally) much more intuitive and reliable. And advanced. They don't have quite the same "Made for Autobahn" feel. While I did love my LS400, it really seperated me from the road. I adored my SC430, but it fell a little short of true "sports car" status. My wife thinks her RX330 is the bees knees, but I find it somewhat utilitarian in its feel and it is getting a little long in the tooth. And while my LX470 seemed indestructable for over 200,000 miles and was an absolute beauty off-road, its on-road handling left an awful lot to be desired. (For you guys who think the GL leans - don't ever drive an LX470!)

I don't know, it's really difficult to weigh all the factors and come up with a single answer. And clearly it's not an easy thing to do because, well, nobody has done it. Like I've said before, at some point you're getting that "smile factor" from your German diesel!

I'm dividing the amount spent to avoid an event by the odds of the event happening.

Remember, I count any repair as a repair. Many GL's have needed to have their door handles replaced. You probably don't have to interrupt a trip for a broken door handle.

I don't know the specifics behind the air suspension failures. Does the system fail in a way that the car can still be driven?

This coming week we'll start previewing the next set of results to participants. The preview results will be updated as responses come in.

As always, the more owners participate, the better the information we can provide to everyone.

Car reliability research

Starting this month we have a new question to measure, as objectively as possible, the severity of a problem. Many people have been asking for reliability stats that weight problems by how severe they are, and once we have enough responses with the revised survey we'll start providing this.

Also this month: updated reliability stats.

We have updated results for the GL-Class to include owner experiences through September 30, 2010. Other sources of car reliability information won't cover the months since April until the summer or even fall of next year.

Repair frequencies, in terms of repair trips per 100 cars per year:

2008: 80, about average, and a substantial improvement from earlier; sample size right at the minimum

2007: 163, worse than average

Thank you, once again, to everyone who has been helping. We'll have further updates in February and May. With more participants, we could provide more precise information and cover all model years.

To see how competitors compare, and to sign up to help:

Mercedes-Benz GL-Class reliability ratings and comparisons

We have updated results for the GL-Class to include owner experiences through March 31, 2011.

Repair frequencies, in terms of repair trips per 100 cars per year:

2008: 89, about average

2007: 128, worse than average

Thank you, once again, to everyone who has been helping. We'll have further updates in August and November. With more participants, we could provide more precise information and cover all model years.

To see how competitors compare, and to sign up to help improve this information:

Mercedes-Benz GL-Class reliability ratings and comparisons

We have updated results for the GL-Class to include owner experiences through June 30, 2011.

Repair frequencies, in terms of repair trips per 100 cars per year:

2008: 134, worse than average

2007: 125, worse than average

We'll have further updates in November and February. With more participants, we could provide more precise information and cover all model years.

To see how competitors compare, and to sign up to help improve this information:

Mercedes-Benz GL-Class reliability ratings and comparisons

I have owned two GL450's : a 2007 and now a 2011.... breakdowns? None
minor nuisance issues handled by warranty? 1 on the 2007. Quality issues? None. Expectations for this vehicle? Met them all. Faith in the vehicle? 100%! Miles: 2007 had 70,000 the 2011 has 8000.

Same with me. I have over 100,000 on my GL and I've made no claims against my aftermarket warranty and only a couple warranty issues. Those were around 88,000 miles. The ones on the warranty had nothing to do with the driveability of the car and I could have done the repairs myself.

We have updated our reliability stats for the GL-Class (on our redesigned site) to include owner experiences through September 30, 2011.

Repair frequencies, in terms of repair trips per 100 cars per year:

2008: 173, worse than average

2007: 112, worse than average

Thank you, once again, everyone who has been helping. We'll have further updates later this month and in May. With more participants, we could provide more precise information and cover all model years.

To see how competitors compare, and to sign up to help improve this information:

Mercedes-Benz GL-Class reliability ratings and comparisons

We have updated our reliability stats for the GL-Class to include owner experiences through September 30, 2012.

Repair frequencies, in terms of repair trips per 100 cars per year:

2008: 118, worse than average -- common problems with air suspension and steering rack

2007: 131, worse than average -- common problems with air suspension and power liftgate

Small sample sizes in both cases.

We'll have further updates in February and May. We'd love to provide more precise stats and cover more model years--just a matter of getting more owners involved!

To see how competitors compare, and to sign up to help improve this information:

Mercedes-Benz GL-Class reliability ratings and comparisons

We have updated our reliability stats for the GL-Class to include owner experiences through December 31, 2012.

Repair frequencies, in terms of repair trips per 100 cars per year:

2008: 143, high

2007: 99, high

Small sample sizes in both cases, which could explain the difference between the stats. Also the 2008s are still under warranty.

Thank you, once again, everyone who has been helping. We'll have further updates in May and August. The more owners participate, the more comprehensive and precise these will be.

To see how competitors compare, and to sign up to help improve this information:

Mercedes-Benz GL-Class reliability ratings and comparisons

Looks like the 2008 is less reliable than the 2007?

This has been the case through the past few updates. But, as noted in the post, I think two factors could explain the difference:

1. Small sample sizes

2. People might have taken the 2008s in just before the factory warranty ended, while they might be letting things go unrepaired with out-of-warranty 2007s.

With more participants we'd have more precise information.

A couple of observations to note:
The data published is the number of failures (or trouble) REPORTED in the various categories. If it doesn't get reported we don't know about it [and we cannot assume failure]. There are a couple of reasons for not reporting:
1) The owner didn't know [or care] that there is a mechanism failures COULD be reported. This likely true for the owner that lets the dealer 'handle everything'.
1.2) It was fixed and not reported
2) It wasn't fixed - and therefore not reported [like MKaresh said: out-of-warranty might equal no fix.
3) Owner didn't know it was broke! eg "I didn't know that light on the dash meant anything" There ARE folks like that!

1. I think the average owner of the GL is fairly well educated and knows how the car is supposed to drive and has a high expectation for the cars performance. The 2007 owners were most likely early adopters which can also be the most critical of a brand.

1.2 This is possible but it would not skew the results to the extent we are seeing with the 2008. I'm thinking the differences are a result of the assembly line's standards slowly relaxing after the initial production push or suppliers relaxing quality control after the first batch because they were not put under the microscope as much as the first batch of cars. A much smaller sample size could also change the results but it could have swung the total opposite way if the owners had more problems.

2. Is highly unlikely. Typically items that brake on the GL have to be fixed or the car is not driveable. Transmission valve plate and air struts come to mind as the most common repairs on the GL's followed by a slew of problems with the 320/350 not seen on the 450.

3. See comment above. Things that affect the GL also affect the driveability of the car. You can't help but notice.

^^ I've seen signs of 1.2 before, where a new model had very few problems at first, but more after an initial period during which inspections were likely more thorough.

We've updated our reliability stats for the GL-Class to include owner experiences through March 31, 2013.

Repair frequencies, in terms of repair trips per 100 cars per year:

2008 GL-Class: 135, high, small sample size
2007 GL-Class: 105, high, small sample size

We'll have further updates in August and in November.

For the details, including the descriptions of reported repairs, and to sign up to help improve this information:

Mercedes-Benz GL-Class reliability ratings and comparisons

We've updated our reliability stats for the GL-Class to include owner experiences through June 30, 2013.

Repair frequencies, in terms of repair trips per 100 cars per year:

2008 GL-Class: 103, high, small sample size
2007 GL-Class: 130, high, small sample size

We'll have further updates in November and February.

To view competitors' scores and descriptions of reported repairs, and to sign up to help:

Mercedes-Benz GL-Class reliability ratings and comparisons

We've updated our reliability stats for the GL-Class to include owner experiences through September 30, 2013.

Repair frequencies, in terms of repair trips per 100 cars per year:

2008 GL-Class: 129, high, small sample size
2007 GL-Class: 122, high, small sample size

We'll have further updates in February and in May. The more owners participate, the more comprehensive and precise these will be.

To see how competitors compare, and to sign up to help improve this information:

Mercedes-Benz GL-Class reliability ratings and comparisons