bips

I'm raising a topic that has been discussed before. The critique in question is this one:
http://www.stephensservice.com/bluet...ssuesproblems/
There was a thread on this diesel forum that discussed the Stephens Critique, and when I came to ask further questions, I mistakenly posted in the S-Class forum, where there was an identical OP. So I came back to the diesel forum, but am reluctant to resurrect that thread, as it degenerated into an insult exchange. So here is my question:

I've just stumbled across the Stephens Service Centre web pages. They alarmed me. However ... I have a 2015 GLC 250d with the OM651 engine rather than the OM642. And I'm not in the US, so comments about how diesels were configured for the US don't apply to my vehicle.

So my question is ... how much of the Stephens material applies to my engine?

To respond to some replies I received in the S-class forum, the GLC is the fairly new SUV based rather loosely on the C-Class. I bought the car new 2½ years ago, and so far it has had its A and B service. Just clocked over 40,000kms / 25,000 miles. A lot of that has been long-distance highway driving, and even my around town driving is higher speed, reasonable distance, not stop-start. Yes, winters in Australia are nothing like northern US and Canadian ones, so that's good, although my location has colder winters than much of the country. And yes, summers here can be hot here, but not unrelentingly so in the most populated areas.

I'm asking partly because I'm at the point where I need to decide whether to keep the vehicle beyond the three year warranty period. I admit that I was a bit naive about MB servicing costs when I bought the vehicle. I'll need to find a decent indy if I keep it. The Stephens critique has made me more nervous about keeping it.

It's easy to get confused when researching the issue. There are some posters who agree with the Stephens position. But there are also people who point out just how many of these engines, both 642 & 651, are in use with no apparent pattern of major failures. So I haven't come to an on-balance view, and I don't understand how much of the critique applies to my engine in my location with my pattern of driving. There was a time when I did my own oil changes, but I'm past that now, and I'd need to pay someone.

Can we have a civilised discussion about the pros and cons of the Stephens critique please?

peter2772000

Stephen doesn't specifically single out the 642, he simply refers to the Bluetec technology, which seems to be the same.
As far as inherent problems are concerned, depends on who you ask. Obviously the vast majority of owners aren't posting here, either because they nothing to gripe about or don't want/need to vent about it on a public forum. Some of us here are, I believe, a bit more paranoid than others in regards to potential problems in regards to the Bluetec. Myself being one of them. But the way I see it, making oil changes more frequently than MB recommends is only costing me more. Running synthetic motorcycle oil is another matter, but if you believe Stephen's reasoning and explanations, cost is the only damage being done.

MB is run by the EPA and bean counters. They want to get thru the warranty period ASAP. After that, you're no longer their problem.

mbdiesel12

I admit the prospect of keeping an OM642 beyond warranty is daunting. I have an extended 7/70 warranty and will abandon any clean diesel in the future. The newer gas engine and hybrid gas mileage increases have come a long way and the increased diesel fuel costs and maintenance just don't make sense to me anymore. CA just raised diesel fuel taxes 17 cents per gallon here. Clean diesels from all manufacturers share a lot of common problems related to the DPF/EGR technologies they require. They're just too complicated for good longevity and reasonable maintenance costs.

After reading the Stephens blog and this link which I posted here several months ago (https://540ratblog.wordpress.com/) my take away for my OM642 is this:
1. Change your oil and filter more frequently (5K to 6K seems appropriate)
2. Use an oil rated for both gas and diesel use. HD diesel oil has typically low wear ratings due to differences in heavy duty engine design needs. They put less load on oils than gas engines.
3. Engine wear and oil viscosity are not always correlated. Look at the very good wear ratings for some 0w20 oils in the link above. It's all about the oil additives. Zinc is only one of them and pollutes our cat systems. It doesn't guaranty low wear.
4. Using high viscosity oils in engines not designed for them can cause bearing failure and less oil flow. Less oil flow can equate to higher oil temps. If we're concerned about engine sludge (IE- oil thickening) why start out with a thicker oil? Gas engines use turbo chargers just like diesels. Why aren't we hearing about failures in them to the same degree? Oil flows through a turbo very quickly before it is cooled and mixed with cooler oil in the pan. If your oil temps are within a reasonable range it shouldn't be a problem. I believe not changing oil frequently enough is our problem.
5. If you're concerned about what's happening with your engine and engine oil send it out for lab testing. That will tell you what you need to know with respect to viscosity changes, wear protection, oil dilution, soot, and TBN. I have about 50K on my engine and my oil shows very well. I use Pentosin Super Performance III 5w30. It's 229.51 rated for my engine. See the link above for it's wear and temperature ratings.

While the Stephens blog has some interesting points I also found the more scientific and engineering oriented information from the link above very useful. We all have to decide for ourselves.

kajtek1

I just inspect the 642 engine with 180k miles on it and beside intake/EGR cleaning I don't see why the engine would not make 1/2 million miles. Then maybe timing chain and turbo rebuild. The engine suck water and I replaced long block, so the old block was good item to inspect.
Sure new technology has more things that require more maintenance and can fail and after replacing the 642 I can say the engine has maze of peripherals and sensors.
Than 651 engine seem much simpler, but read my topic about DPF, who is another high-priced wearable on the car. Can't have the high-performance + high efficiency and high reliability.
Iphone will never have dial-phone reliability (have friend who use theirs for 60 years)

geniushanbiao

I can't agree with your point 4. Yes there are also turbos in gas engines, but gas engines don't have to run the DPF regeneration, which makes the turbo glow red. Gas engine turbos also fail early. Take a look at those 1990s-2000s Audis and BMWs it's not uncommon to see a turbo fail in those cars. I've seen many Audis turbo fail around 150k miles. The reason you don't hear those is that the life span of gas engines is much shorter than diesel, expectations are different. Most of time when the turbo fails on a gas engine, it already has ~150k miles or so that the owner knows it's time to replace the vehicle. But on a diesel most are expecting at least 1/2 million miles so it makes sense to fix the failed turbo.