When I first wrote this article four or five years ago, it was just a way to help my local BlueTec diesel owners better understand the rumors & problems Mercedes-Benz was having with this engine.      I thought if owners understood how a BlueTec diesel worked, they would understand the value of preventive maintenance.     My first task, was convincing owners that Mercedes-Benz wasn’t telling them the best way to maintain this engine.    Ten & twenty thousand mile oil change intervals with “low SAP’s” diesel oil was a one way trip to the salvage yard.     I know, I know, there are owners claiming they’ve gone 600000 miles with no problems.    If you remember the “Bell Curve” from your college days, those 600K owners are way, way over on the far right side of the “Bell Curve”.     Frankly, I’m not sure even the Bell Curve stretches that far.   I quickly realized, that most owners didn’t care about understanding this engine.    They weren’t interested in maintenance, they just drove it until it quit.     In the early days of this engine, owners thought Mercedes-Benz would never mislead them.    If Mercedes-Benz recommended 20000 mile oil changes, that was gospel.    Plus it cost less…. for a while.
Now new owners stumble onto this website after they bought a BlueTec.     Someone told them they better wake up, or they would be sorry.    The original BlueTec owners are mostly gone.    Their engines locked up years ago.      New owners are rightfully scared of what they now own.     Those original owners took out their revenge on Mercedes-Benz’s reputation, & the problems with the BlueTec are all over the internet.
The BlueTec diesel is the most complicated & least understood engine Mercedes-Benz makes.     The average mechanic hates working on them, because they are a guaranteed comeback with a mad customer.     It’s way easier to make money on other models & Mercedes-Benz treats a BlueTec diesel mechanic like he’s the one who built this mess.    Where the owner lives & how they drive, makes a big difference in reliability.     One owner never has a problem, while the guy down the street is bouncing from shop to shop with nothing but huge repair bills to show for his effort.     How does that happen?   I understood the problem & how to deal with it, but explaining it to a owner was a different matter.   No matter how many times I rewrote this article, I couldn’t fine a concise way of explaining all the nuances of a BlueTec diesel.    As the years went by, I kept trying to find a better way of explaining this.
This engine & its emission system is a lot like a onion.    Every time I think I finally understand it, I discover a new level of complexity.    Anyone that tells you they understand a BlueTec diesel, hasn’t been around enough of them.    Somehow, BlueTec owners found my feeble attempt to explain the OM642 BlueTec diesel.    I’ve also  noticed this article has caused quite a stir on various owner’s forums. I feel bad for owners who really don’t know what’s going on.     They get on a forum looking for answers, & they get blasted by the forum “know-it-all”.    It’s always the guy that knows just enough to sound like he might be right.    I have no idea why they’re carrying water for Mercedes.    These guys question the things I talk about.     They claim there is nothing wrong with the BlueTec diesel, & the factory maintenance is great.    I’ve repeatedly offered to substantiate anything I’ve said, but no one has ever ask.    I can support everything I say, with Mercedes-Benz own documents.     Everything.
A few years ago, my mechanic’s started complaining about all the phone calls about this article.    “Why are we helping people we will never see?”    “Let their local Mercedes dealer answer their questions.”
They had a point, but I didn’t have the heart to take the article down.

Five years later, & I’ve retired.       I had the business number roll over to my cel phone.   I didn’t want to just abandon my old customers.     But that also meant I kept getting phone calls from this website.   No one was more surprised than me.    As you know, there are plenty of people complaining about BlueTec diesels, but there’s not much in the way of help.    Mercedes-Benz publishes a lot of technical information, but they don’t make it easy to find.     They are also bad about explaining things in plane English.    Mercedes also publishes a lot of conflicting information.    I often wonder if they actually read what they publish?    Over the last 4 or 5 years, I’ve spoken with at least 1000 BlueTec owners.   I’ve tried to focus on the issues that effect most owners.    Lately, a few people have ask what qualifies me to pontificate about the BlueTec diesel & its problems?     I grew up in a small Indiana farm town. Self promotion or bragging, was not an admirable quality.    In those days, you just did what you said you would do.   If I didn’t, everyone knew my Mom, & she definatly knew where to find me.     So for what it’s worth; in 1967, I got a job at the Mercedes-Benz dealer in Indianapolis.   In those days, you could actually work your way through college.     I was a Mechanic, Shop Foreman, & a Training Instructor.    Finally, I was the Service Director for two Mercedes-Benz dealerships.    Mercedes-Benz gave me the “Star Technician” award once & the “Mercedes-Benz Service Manager of the Year” award 5 times.    Twenty-five years ago I started my own Mercedes-Benz shop.    I retired at the end of 2017.  

Mercedes-Benz installed the BlueTec Diesel in passenger cars & Sprinter Vans.    They also put it in Dodge Vans, Freightliner Vans, & Jeeps.    Regardless of which body it went in, all BlueTec’s work the same way.    When Mercedes first came out with the OM642 diesel in 2007 & 2008, they called it a “BlueTec”.     It wasn’t.     “BlueTec” is the name of the emission system which has a DEF (Diesel Exhaust Fluid) tank.     Also known as “AdBlue”.     (Mercedes loves its acronyms.    For normal people who are not into all this tech stuff, I’ll try to explain them as I go along.)         2009, was the first year Mercedes-Benz actually had DEF fluid or AdBlue, injected into the exhaust.      They inject the DEF into the exhaust to reduce emissions.      Except for the DEF fluid, all OM642 V6 diesels operate the same way.     From day one, all OM642 diesel’s have a DPF, (Diesel Particulate Filter, which traps the black soot in diesel exhaust).      The engine does not need the DEF or the DPF to operate.     Then why does the engine run to badly when something goes wrong with the DPF or DEF systems?     When the DPF or DEF has a problem, the DPF or DEF computer tells the engine’s computer to stop running properly.   Mercedes calls this “Limp Home”.      When the engine switches to “Limp Home”, it lacks power.     Warning lights come on, & if you ignore the warning lights, the engine’s computer (ECU) finally won’t allow the engine to start.    Mercedes admits that 100% of the 2009 to 2015 DEF fluid tanks will fail.     That’s right, 100%.
All Mercedes diesels have exhaust driven, air / oil cooled Turbochargers.     Why is this important?     A Turbocharger forces more air into the engine than if it wasn’t there.     That gives the engine more power.     But something has to turn the Turbocharger.     Engineers use the engine’s own exhaust gas to spin the Turbocharger.     The faster you accelerate, the more exhaust is created.    The faster the exhaust flows, the faster it turns the Turbocharger.     So why is this a problem?     The exhaust gas is real hot.     Remember the DPF?     Every so often, the engine has to burn off the soot trapped in the DPF.     To do that, the engine’s computer injects a lot more fuel to heat up the exhaust, & “regenerate” the DPF.    Now we’re really cooking.     In fact, when you’re driving up a steep mountain & you’ve got your foot on the floor, the exhaust gas can also climb to over 1600F.      That means the exhaust gas is also heating your Turbocharge to over 1600F.      This is technically known as “Red Hot”!     There are some people who don’t want to believe this.      I invite you to the Garrett Turbocharger website.   Garrett & two other companies make the Turbocharger’s for Mercedes-Benz.      Read the Garrett FAQ section.     You would think Mercedes could have thought of a way of a better way to cool your Turbocharger?    They did, they just didn’t put it on your engine.    Your Turbocharger is lubricated & cooled with the same oil that’s inside your engine.     As soon as your engine oil enters your Turbocharger, it is super heated to a temperature far beyond what the oil was ever designed for.     This is why Mercedes is having so much trouble with the engine oil.   It doesn’t take long before all the oil in the engine is boiling hot.    This is also why the NOACK volatility number for the engine oil is so important.    (More about NOACK later.)   People think synthetic oil should be able to solve these problems.   Just because an oil is synthetic, doesn’t mean it was designed for this kind of heat.

Other than oil & air, there is nothing else cooling your Turbocharger.     Why would Mercedes build a engine with such a obvious problem?     You know the answer, “money”.      Garrett makes water cooled Turbochargers that run cool.    They also make Turbochargers that have their own separate oil tanks with special Jet engine oil that’s designed for extreme temperatures.     Mercedes even offers these Turbochargers on military & emergency vehicles.     But those aren’t available to the public.     The cost of a proper Turbocharger would add another $3000 to the vehicle.    If your BlueTec had a water cooled Turbocharger, most of its problems would disappear.    The oil wouldn’t vaporize.    The EGR & intake system wouldn’t sludge up.   You could actually go 10000 miles on an oil change.    20000 mile oil changes are just stupid, & Mercedes should be ashamed of themselves for telling their customers to do this.

But the OM642 is what it is.     How do we solve the problems with the OM642 with the way it is?   After 10 years of idiotic oil change intervals, Mercedes-Benz is finally recommending the BlueTec diesel oil should be changed twice a year.   For 2018, Mercedes now says: {{The low temperature characteristics of engine oils can noticeably deteriorate during operation, e.g. from aging, soot and fuel accretion.   For this reason, regular oil changes using an approved engine oil from the suitable SAE classification are urgently recommended.}}   Now, oil changes are “urgent”.     What happened to 20000 miles?    Do you think Mercedes is making any effort to inform the owner’s of previous model years about this sudden “urgency” for regular oil changes with a “suitable” SAE oil?    In fact, what exactly is a “suitable SAE classification”?    Is it a MB229.51 oil?    A couple of years ago, Mercedes said the MB229.51 oil was no longer approved.    Now it’s back.    What’s the difference between MB229.51 & MB229.52?    Are they a “suitable SAE classification”?    In the 2018 BlueTec owners booklet, Mercedes shows a chart with “approved SAE oils” that have a viscosity of 20W/50 & 10W/60.    But there are no “low SAP’s” oils in those viscosity ranges.    Mercedes doesn’t have any approved MB229.51 or MB229.52 oils with 20W/50 or 10W/60 viscosity.    I know what they are trying to do, but the average owner & dealer are left scratching their heads.    Why is it so hard for Mercedes-Benz to explain this in plain English?    Maybe it has something to do with Mercedes oil contracts with Mobil?     You’ve seen that Mobil One sticker on your engine?   It didn’t get there by accident.    You have no idea how much that sticker has cost you.     Mobil One doesn’t have a “low SAP’s” 20W/50 or 10W/60 oil.    Right now, it is 110F, & Mercedes-Benz dealers in Phoenix are still putting 0W/30 Mobil One ESP in BlueTec diesels.    They are still telling owner’s they can drive 20000 miles on 0W/30 oil.    0W/30 oil, is for the dead of Winter at the Arctic Circle.  Mercedes sends out tons of advertising to their customers.    Do you think they will ever tell any of their BlueTec owners about their 2018 “urgent” recommendation?    Do you think Mercedes has told their dealers, to recommend a BlueTec get the oil changed at the start of summer & winter?    Ask your Service Advisor if they know anything about this?     No more 10000 & 20000 mile oil change intervals.  

Because of Mercedes new 2018 maintenance schedule, I’ve dropped my tedious explanation of diesel oil specifications.     It was just to confusing & it appears the EPA, Mercedes-Benz, & the oil companies now agree.     I don’t think any of them have officially given up on “low SAP’s” diesel oil, but I think they’ve decided to look the other way.    Whatever it was, something changed in 2018.       Oil companies are now formulating new diesel oils with chemical properties that are similar to their motorcycle oils.   Owners are nervous about using Motorcycle oil in a diesel engine.    I understand, & I wish the industry did more to inform the public about the actual differences in these products.   A Ester based Motorcycle oil is a higher quality than diesel oil.   Ester based Motorcycle oil has a better additive package & can withstand extreme heat & pressure better than most diesel oils.     High performance motorcycles run at twice the RPM’s of a diesel.   Motorcycles have small crankcases with small cooling systems.   Motorcycle oils get very hot, just like BlueTec diesels.   Premium motorcycle oils have much lower NOACK values than diesel oil.    I’ve heard from a number of Petroleum engineers who have been gracious enough to share technical articles.     One engineer sent me information about a new diesel oil with an extraordinary Material Data sheet.     Another sent me a new redesigned billet OM642 oil filter housing that supports a much bigger oil filter.   It works better on the Sprinter, because there is more space to work with.      It is easy to install & it greatly improves oil filtration.     You can check it out at www.pktfilterinsert.ca.
Anyone that wants written proof of anything I’ve said, send me a email & I will forward you the documents.      

This article has taken on a life of its own.    Now that I’ve retired, I’m getting even more calls & emails, & they’re from all over the world.     In this article I’ve tried to give people solutions to their BlueTec problems.    But a lot of people want more.    This is complicated for a lot of owners & they want a personal explanation.     Even though Mercedes put the OM642 in a lot of vehicles, Sprinter owners contact me the most.     Sprinters hold their resale value much better than anything else Mercedes-Benz sells.     Sprinter owners tend to be more proactive.     They either use their Sprinter for work or for travel.      They can’t afford breakdowns.      Sprinter owners also tend to be more concerned about the environment.     If the OM642 is well maintained, the emission system works better.      I know for a fact, this engine reacts well to good preventive maintenance.      It will pay for its self 10 times over.   People are now starting to say these new diesels are throw away engines.    They think there is no way to keep them together.     I strongly disagree.     The problem is, nobody will tell owners the proper way to maintain a OM642 diesel.     Mercedes did a much better job explaining the maintenance in their 2018 Owners manual, but they are still a long way from the plain English the average owner needs.     Then you have dealers that still won’t change.    Every day, owners tell me their dealer is still telling them they can go 20000 miles on oil changes.    

I’ve spent so many years helping people with these diesel problems, it’s hard to retire & just switch it off.     However, I can’t spend my retirement answering phone calls & emails.    I would rather spend my free time with my one & only two year old Grandson.    I’m starting to like this Grandpa thing.   But then one of my old customer’s came up with a good idea.     I can still use my experience to help diesel owners & my Grandson.     I don’t need the extra money.   I would rather have the free time.    But I’m highly motivated to see that my Grandson gets a college education.     It’s hard now to succeed with a college education.   I can’t imagine what it will be like in 18 years, but it won’t be easier.    To fund his college savings plan, I’m willing to help Mercedes diesel owner’s with their problems.    For a long time, I freely answered people’s questions & sent them as much technical information as they wanted.  People would call me with all sorts of questions.   This stuff is hard, & there is not much help out there.   I’m sympathetic, but I already did my 50 years.     If not for my Grandson, I would let the website expire.     So, for $200, I’ll help BlueTec diesel owners with their problems.     I’ll answer all your questions & give you a written plan with exactly what to do.   I’m currently getting about 15 calls & emails per day.     I originally thought I could do this on the honor system, but that didn’t work.    Some people sent me dozens of emails & phone calls.     They would send me their repair orders & estimates for thousands of dollars in repairs.    After spending many hours helping them sort through all of their problems; you guessed it, they forgot to send the money.     Then there are the guys who’ve taken their engine apart & can’t get it back together.      They want me to talk them through it.      They also forgot to send the money.     It went on & on late into the night.     About half the people appreciate the help & sent the money.    Now I’ve set up a PayPal account to fund my Grandson’s college savings account.     If after reading this article, you want more help, you can email me at ‘tom54stephens@gmail.com’.     Let me know what your problem is.     If you just want a maintenance plan, tell me where you live & how you drive.    Tell me your model & year.     How many miles & a brief service history.      If you are buying a new or used Sprinter, I’ll help you with that.    For $200, I’ll answer all your maintenance questions & I’ll answer your future questions.     I’ll explain it on the phone or email you all the instructions.    I will send you a lot more detail about these BlueTec problems & how to solve them.   I want people to understand the complete picture, because it makes it easier to avoid expensive repairs.    All the horror stories you read about, are totally avoidable.    You really can live with this engine, it just takes some extra effort.
I’ve tried to answer most of the typical questions in this article.      (I apologize for rambling.    I often think of things & add to this late at night.)     Lots of people are baffled by all the misinformation they get.    I will send you a lot of technical stuff that explains the problems in detail.    But if you only want a simple answer, I can keep it simple.    I’ll tell you where you can buy all the things you will need.      (By the way, I don’t make anything off of what I recommend.    I also don’t put any of those annoying Google Ads on the website.)      I’ll explain what oil to use for your specific situation.     There is no one oil that works for 100% of the vehicles.      If you’re having the early warning signs, I can tell you how to prevent a $30000 disaster.     There are other common failures that I can save you thousands even after it’s failed.     Proper maintenance is not cheap, but it’s way cheaper than a new engine.     I want you to avoid being one of those You Tube video’s of Mercedes diesel problems.   Please don’t call just to get free advice on what oil to use or why your car won’t start.   Find a good mechanic & support him.
I’ve spoken with a large number of owners & heard their stories about their experiences with their local Mercedes-Benz dealer.    If I retold these stories, people would think I have some bitter agenda.  To be honest, it is shocking how little dealers know about this engine.   There are just to many stories, from all parts of the country, for this to be a fluke.   There are dealers telling owners, that there is no such thing as an Oil Separator.   Dealers arbitrarily tell owners there are no software updates for their vehicle.   Mercedes-Benz knows how important the updates are.   They know exactly how many updates are needed & exactly how many are actually preformed.    I would be surprised if 5% of the updates are actually performed.   Mercedes sends out the bulletins; dealers won’t read them, or they just don’t care. If you plan on driving a Mercedes-Benz vehicle with a OM642 or OM651 engine, you need to educate yourself on how this thing works.   If you don’t, you will pay dearly for someone else to stumble around under your hood.    Even if you educate yourself, it will still be very hard to find competent service.   If you find a consciences dealer or mechanic, count yourself as very lucky.  

People have been told to protect the DPF at all cost.     The DPF is no big deal.     It can be cleaned or replaced.     The engine is a big deal.       The priorities are backwards.     I’m going to explain this, so it makes sense.    You won’t have to believe someone at the dealer who knows even less than you.     If you want to figure this out on your own, or let your dealer answer your questions; go right ahead.    You’ll not hurt my feelings.     If you think $200 is to much, Mercedes charges $60 for 24 hour access to their technical website.     It’s web address is; cvtekinfo.com.      Knock yourself out.       If you think your BlueTec is confusing, wait until you waste a day on their website.       If you’re looking at a New Sprinter, I can tell you what options you’ll want & which ones you don’t.   For example, you don’t want Xenon headlights.   When they burn out, they can cost thousands to repair.     You can make the standard headlights just as bright as the factory xenon for a fraction of the cost.    Valet or Shuttle companies should avoid the BlueTec.   Why, Sprinters make perfect people haulers?    The drivers often let the engine idle for long periods to keep their customers cool or warm.    The drivers themselves, will set in the Van & let it idle while their passengers are attending some event.   Mercedes now admits in their 2018 Owners manual, that idling is a huge problem for the BlueTec diesel.   Yet Mercedes sells the Sprinter Van to Fleet companies, knowing full well that they will have major problems.   If you are buying any new vehicle with a BlueTec diesel, buy the maximum warranty offered.   Only buy the Genuine Mercedes-Benz warranty.   Keep all your records.   Only use genuine Mercedes-Benz filters.   If you’re buying a motor home, only buy the Mercedes-Benz extended warranty.   Buy all the towing coverage you can buy.   I have no idea how a motor home dealer can diagnose problems with a Sprinter.   Mercedes dealers barely keep current with training.   I have no idea how a RV center can afford to send mechanics to all their different brands & buy the factory diagnostic equipment.   I hear from RV owners who wait days for someone to even scan for fault codes while they are broken down.   RV owners have spent a great deal of money & they have no idea how shallow the knowledge pool is at these RV centers.

Mercedes is constantly sending out software updates for their computers (ECU).    Even their newest Vans have important software updates.   Dealers don’t like doing the updates because Mercedes doesn’t pay them enough.    It takes their best mechanic to do the updates.    If a dealer did all the updates they should, they couldn’t afford to pay their mechanics.     I can explain how you can work around them.     Having the dealer to do the updates is the best choice, but if they won’t…… 

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WHY IS EVERYONE SO UPSET WITH THE BLUETEC DIESEL?    Mercedes diesels have great power & excellent fuel economy.    They drive better than another Van on the market.    I love Sprinters.   The SUV BlueTec diesels….. not so much.    The SUV’s depreciate so fast, people are upside down & it’s hard to justify spending more money to save them.
On the other hand, Sprinters are unique in the marketplace.    They have long useful lives & are worth the investment.     I totally understand why people like Sprinters.     But why are there so many complaints?    Most people buy a BlueTec & they believed the salesman when he said they can go 500000 miles with no problems.     I’ll bet the salesman didn’t tell you Sprinters take special maintenance & special mechanics to work on them.     The average owner is not prepared for the maintenance cost & the aggravation.      If you’re reading this, your part of a tiny group of owners who will actually do the maintenance if someone actually explained it.
A BlueTec diesel is way more complicated than any other Mercedes made.     Routine maintenance is more expensive.     Any mechanic that truly understands a BlueTec is extremely skilled.     He is typically the smartest guy in the shop.     If you find a good BlueTec mechanic, he’s good as gold.     But even the very best BlueTec diesel mechanic will have comebacks.      Most dealer mechanics won’t work on a BlueTec because they can make more money working on easier models.      Who needs to listen to mad customers blaming them for inherent design problems that aren’t the mechanics fault.
At first, proper maintenance will seem like it’s more expensive.      I can assure you, it’s way less expensive than a new engine.    When you hear some guy telling you nothing has ever gone wrong with his diesel in 300000 miles, it isn’t true!    In the past, Mercedes didn’t want to tell owners about the proper maintenance.     They thought it would cost them sales.    Finally Mercedes is slowly coming around.

The proper engine oil is a major factor in the life of a BlueTec diesel.     Mercedes published a great service bulletin in 2008.    That bulletin tried to explain away the most fundamental problem a BlueTec diesel stills has to this day.     The bulletin talks about oil from the crankcase being sucked into the Turbocharger.    Mercedes said it wasn’t a problem.     Well, it was & still is a problem.     Mercedes has never fixed the cause of oil entering the Turbo.     They’ve put band-aids on the problem, but it’s that oil entering the Turbocharger, that causes the EGR, Swirl Flaps, & intake system to get so dirty.     Stop the oil going into the Turbo, & lots of other problems go away.

How does the oil get into the Turbo in the first place?    Here’s the simple answer.     The Turbocharger is exhaust driven.    During DPF regeneration, hot exhaust gas is used to burn out the soot in the DPF.     If you’re driving a big heavy Sprinter in the mountains on a hot Summer day, & the DPF decides to regenerate, the exhaust gas can reach 1600F.   That same exhaust gas is also heating the Turbo to 1600F, & the engine oil in the Turbo is also heating to 1600F.   (Regeneration of the DPF is what burns off the soot trapped in the Diesel Particulate Filter.    In order to burn off that soot, the engine’s computer injects extra fuel.    Not all of the fuel is burnt.   Some gets past the piston rings & into the crankcase oil.    Mercedes calls this “fuel accretion”.    That’s “fuel dilution” in plain English.   Whatever you call it, it makes a big mess inside the engine.   This is also why Bio Diesel is such a problem.   When it gets into the crankcase oil, you’ve really got a mess.)
Some people don’t believe the Turbo can get to 1600F.    BELIEVE IT!    I can show you Mercedes own technical test data, & they admit it gets that hot.    People don’t realize how hot 1600F really is. Remember that frying pan you cooked your breakfast on?   If you heated it to 1600F, it would be a unrecognizable blob of metal.    Now pour a quart of your favorite oil on it (when your wife’s not home) & watch what happens.    The Turbo is lubricated with the engine’s oil.  That means the engine oil gets so hot, it turns into steam.     The hot oil vapor is to much for the engine’s one undersized Oil Separator to handle.    The Turbo is sucking air from anyplace it can, & that hot oil vapor is sucked into the Turbo.    This is why you want super clean air filters.   You want the Turbo sucking air into the engine, not oil vapor.    Mercedes knows this is a problem, but yet they send out service bulletin (S-B-09.20/29) saying it’s normal.   “It ain’t normal!”   The engine only has one Oil Separator.    (On American engines, they call this the PCV valve, & they have two.)     Mercedes only gave the engine one Oil Separator.     The Turbocharger should have been water cooled & its own oil sump with jet engine oil.    But, Mercedes went cheap.    Military Sprinters have a water cooled Turbocharger.    The Military has a distinct advantage over the average owner.   When the Military has a slugged up engine claim denied, they send in a SEAL team to ask “why”.     Everyone else, “it’s normal”.    As the oil vapor goes into the Turbo it exits into the exhaust.    The EGR (Exhaust Gas Recirculation) grabs part of the oil vapor in the exhaust & sends it back into the air intake system to be burnt again.    That oil vapor keeps building up on everything in the intake system & it finally turns into a hard carbon deposit.    This “crud” finally blocks the air flow & turns on the check engine light.     In the mean time, the oil in the crankcase keeps getting thicker as the oil vapor is boiled off.    Mix into the crankcase oil a bunch of extra diesel fuel that has washed past the piston rings & you’ve got yourself a real bucket of sludge in no time.     While this is happening, the poor timing chain is trying work in this mess.     The chain stretches, & that’s the rattle noise you hear after a cold start-up.     As that tar / sludge builds up in the engine, it restricts the oil passages to the crankshaft.    The crankshaft finally starves for oil & the engine locks up.    As they say in France, “Voila”, it’s off to the salvage yard.

The key to understanding oil, is in the Oil’s Material Data sheet.     It tells you what the oil is really designed to do.     People often say their old car did just fine with Mobil One, & that should be fine in their diesel.     Gas engine’s don’t run extreme oil temperatures.     Low “NOACK volatility” is the most important oil spec.     It tells you how much of the oil will turn into steam when it gets hot.     It’s the hot oil vapor that is killing your engine.      Here’s another tip; if the oil company doesn’t publish a Material Data Sheet for their oil, forget it.    If they have a Material Data Sheet, but it doesn’t say about the NOACK volatility, it means they don’t want to tell you it is the maximum the government allows, 13.5%.      (The NOACK volatility causes pollution.   Oil companies cannot exceed a 13.5% NOACK value.    Any oil that’s at the maximum, is not a very good oil.    Mercedes does not publish a Material Data Sheet for their oil.)      If you want to waste some time, call the Mobil One help desk & ask them what’s the NOACK value for their 5w/30 ESP oil?    They refuse to give consumer’s that information.    They must be real proud of that oil.
Motorcycle oils typically have the best NOACK volatility scores.     But, there are some new diesel oils that have copied the chemical make-up of the best motorcycle oils & have improved on their NOACK volatility scores.    Improved “diesel” oils are coming out every day.   So far, the best ones have a NOACK value of 3.7%.

WHAT GOES WRONG?    Proper oil is just part of the solution.    BlueTec “clean diesel technology” is anything but simple.   Stop & go city driving in cold weather, is the worst possible life for a BlueTec.   Also, never let a BlueTec idle for long periods.    It is very hard on the engine.    When you first start it, give it a few seconds to wake up, & start driving.     From an emission control standpoint, cold weather is also the toughest to meet.
This is the area that’s causing all the legal trouble.    The EPA believes in a “one size fits all”.
Mercedes sells the same BlueTec engine in Canada & in Phoenix.      There is no way this engine can run with the same maintenance in both climates.     To meet emission controls in cold weather, they need to get the engine up to operating temperature as fast as possible.   A quick warm-up & fuel economy, are the reasons for very low viscosity engine oil (0W/30).   It’s also the reason for the belly panels under the engine.    Mercedes says the belly panels are for “noise encapsulation” & to protect the fan belt from road dirt.    The belly panels are really there to trap the heat during warm-up.    The problem is, the belly panels add to the extreme heat after the engine is hot.     Mercedes has also finally woken up to this.    They have stopped putting the belly panels on.

Many owners think they can treat a BlueTec like a gas model.    I’ve heard diesel owner’s brag about using the cheapest oil they could find at Walmart.     Go ahead.     By the time you run that oil for 80000 miles, you will be out of warranty & you can take all that money you saved, & pay the tow bill to the Salvage Yard.      Before a mechanic can fix your current problems, he really needs to clean up all the past neglect.     He has to have a good baseline to begin.    He needs to download the newest software into the various control modules.   A lot of customers just can’t believe they need to do all this stuff, just so the mechanic can begin to solve your initial problem.   Owners think it’s a scam, & they won’t pay for it.    An inexperienced mechanic tries to please the customer, & he tries to work around the other problems.     He’ll finally wish he hadn’t let the customer tell him how to fix the problem.    A good BlueTec mechanic won’t even start chasing your problem, until he has a solid baseline to work from.    People are constantly asking me if I know a good BlueTec mechanic in their area.   This is how you know if a mechanic is experienced. Customers bounce from shop to shop, because no one wants to face the fundamental problems. You have a filthy mess that must be cleaned up before your problems can be solved.     You may even think your car is covered by an extended warranty & you don’t have to worry about any of this.    Warranties won’t pay for cleaning up the mess.   In fact, this is so bad, Service Contracts won’t even write coverage on a BlueTec diesel any more.    After multiple visits to your dealer & the mechanic has thrown thousands of dollars at your problem; even Mercedes-Benz won’t pay the bill.   (This is where I really think Mercedes owes it to their customers to explain these problems or pay to fix them.    Instead, they would rather spend their money litigating with the DOJ or their customer.)     Mercedes kicks back your warranty claim & the dealer gets to eat the repair bills.    Or better yet, the dealer blames it on bad fuel & makes you pay for everything.     Oil leaks are a particular problem caused by the extreme heat, dirty air filters, & boiling oil.     {Once the engine starts leaking oil, there is no cheap way to fix the problem.    I’ve come to the conclusion that owners are better off if they ignore the oil leaks.   Continue to change the oil & air filters, but just drive it.   Oil leaks are “generally”, to expensive to fix & do them properly.    There are a few tricks to prevent oil leaks that I can explain later.}    Under warranty, Mercedes-Benz won’t pay for cleaning the diesel oil mess & neither will the customer.   Mechanics are sick of trying to work around all the crud, so they do a half ass fix just to get rid of you.    There are seven or eight known oil leaks that I can show you how to prevent or at least slow them down.
Owners email me all the time, saying the dealer wants them to pay for what should be a warranty repair.   The dealer blames it on “fuel contamination”.    “Fuel contamination” is dealer code for “we’re sick of working on your BlueTec & we’re not spending any more of our money to fix it”.     When you hear that, start haggling with the Sales Department for a trade-in on a new “gas” model.     Never buy a used BlueTec diesel!    Stop calling me & telling me about the good deal you’ve found on a used BlueTec with a slight ticking noise.     If someone gives you a BlueTec for free, it’s still not worth it.   The cost of cleaning one up & fixing all the known problems, will quickly exceed the value of the car.    The only exceptions are Sprinters.   Even with a bad engine, they could be a decent vehicle.   Remember one thing.   Just because you install a new engine, that doesn’t mean everything is new again.   You can still have a money pit if the vehicle has been neglected.     $30000 for a new engine, then $7000 for a transmission, $2000 for a DEF system, & $2000 for a DPF, are some of the other repairs you can face.

All diesel engine manufactures must comply with the same regulations.   This is not unique to Mercedes-Benz.   To comply with the regulations, engineers had to increase the diesel combustion temperature…. a lot!    But, American Diesel engine builders went with a different style crankcase ventilation system (PCV) than Mercedes uses.    The Mercedes BlueTec crankcase vent system is inadequate for the engine.    It’s the main reason American Diesel engines don’t have the problems Mercedes has.
This is where things start getting complicated, so I have to assume you have some technical knowledge or this would take forever  to explain.    If owners did a few basic things when their BlueTec was new, they would eliminate many of the BlueTecs problems.   The right engine oil is the key to BlueTec happiness.

Most of the problems with the BlueTec engine & its emission system are all related to each other.
Once the problems start, it’s a cascade effect.    Often we would see a car for the first time with the Check Engine light on.    The customer just wants to fix what’s wrong, & nothing else.    They don’t want to hear any story about maintenance.    To properly diagnose a BlueTec diesel, the engine will need a through cleaning.    Fluids & filters need to be current, i.e. clean.
Diesel engines have always been dirty, but a BlueTec is a new level of dirty.      It’s often hard to know how slugged up the engine actually is inside, but I can assure you, it’s slugged up.     You will never see it in the oil filter or through the oil cap.      The first thing, add “engine oil flush” to the old oil before you drive to the shop for its oil change.     You can get “engine oil flush” at any parts store.     This will loosen the sludge & let it drain out.
If it’s real dirty, there is a completely different procedure.      Ideally, you want to avoid taking half the engine apart just to clean it up.    Do a search on You Tube for mechanics cleaning up the mess in a BlueTec diesel.    It is a unpleasant experience.     Send me a email, & I can explain how to clean up this engine.    Do not wait until the Timing Chain starts rattling, or it will get much more expensive.

It also helps to simply clean-up all the caked on oil grime on the exterior of the engine.     Oil leaks are common.   But look around the injectors for black sludge around one or more injector seals.   If that has started, there are a couple of ways to deal with this, so send me a email & I can explain in more detail.   Take the top plastic cover off the engine & pour Simple Green all over the engine.   Down in the “V”, there is always a lot of crud.     Spray Simple Green all over the bottom of the engine.    It’s easiest at a quarter car wash, but you can’t blast the engine with the high pressure.    Set it to a softer setting & wash off all the dirty grime.    It will drain out the drain holes in the “V”.    You can high pressure the bottom of the engine.

Software updates for the engine control module, must be current.    If you have strange problems & warning lights, you will go nuts trying to figure them out.     Always update the software first.     Mercedes has updated the software for some of the BlueTec ECU’s, 23 times at last count.     Most dealers don’t want to check of your software for updates.     They loose money doing it.     There are many problems with the old ECU software.    One of the biggest problems, is it injects to much fuel for regeneration of the DPF.     Excess fuel washes past the piston rings & dilutes the engine oil.    This is called”fuel dilution”.
Never run Bio-diesel.    Not even B5.    When it gets into the crankcase oil, it really turns to sludge fast.
The Air Filters also get plugged up very easy.    Early BlueTec’s have 2 air filters.    Later models have one.    One filter is better.    Sprinters have one air filter.    Dirty air filters send the crankcase pressure into orbit.   The more pressure in the crankcase, the more oil leaks you’ll have.   Mercedes has upgraded their air filters several times.
The Oil Separator has been updated 11 times at last count.     It’s the Oil Separator that allows the boiling oil vapor (NOACK Volatility) to be sucked out of the engine & into the Turbo Charger in the first place.    This is what they call the PCV valve on American engines.
The plastic Air Intake at the Turbocharger also melts from the extreme heat.    The hot oil vapor that was “normally” going into the Turbocharger; instead leaks onto the Swirl Motor & shorts it out.    That causes the engine to go into the Limp Home mode.     Oil then drips out the drain holes in the block & all over your driveway.     If you’re really lucky, the metal flaps in the Swirl Valve break & get sucked into the engine.
Mercedes admits to Timing Chain failures on all 2010 to 2015 OM642 Diesels.   Zinc in motor oil helps prevent the Timing Chain from failing.   (1600 to 2000 ppm of zinc is a good number.)   “Low SAP’s” diesel oil has 500 ppm.
Once again, it’s a cascade of problems that starts with poor quality oil & dirty air filters.   There are many other important qualities motor oil needs to have, but these are the basic things.

When a new customer comes in with the Check Engine light on, it’s not just a matter of fixing what the fault code says.   All the basic maintenance of the engine must, I repeat, must be clean & in good working order.    This is the number one reason these cars don’t get fixed on the first attempt.    The mechanic is trying to make the customer happy & keep the cost down.   So he tries to fix the symptom & not the cause.    The customer doesn’t want to spend the money on proper maintenance & tells the mechanic everything is in great shape, when it’s not.     Find a good mechanic & stick with him.    Even when he makes a honest mistake.     It’s very important that all the software is current in all the control modules.    Some dealers don’t like doing this & will tell you it isn’t necessary.     Before you start chasing problems, the software must be current.    When you have hard problems to solve, your mechanic needs a good maintenance baseline.     Ignore this, & you will waste time & money like you won’t believe.    Speaking of Fault Codes; they are often wrong.    The fault code may say sensor “X” is bad.    In reality, it’s sensor “U” that is bad.     I’ve kept hundreds of these fault codes & what the problem really is.
Almost all of the important parts on this engine have been updated by Mercedes to solve some sort of emission or oil leak problem.    Almost any problem the BlueTec has, is a result of the same core design problems that bedevils every BlueTec made.   It’s likely you’ll need to replace many of these parts at some point.    Starting with model year 2014, Mercedes started using a 13.5 quart oil pan.   Those engines are much better than the older 8.5 quart oil pan.

Depending on where you live, you can have completely different issues.     If you live where it’s often below freezing & make short trips, there are 5w/30 oils with very good NOACK volatility.
Much lower than the official Mercedes-Benz oil.      In subzero weather, change the oil every 3000 miles.     Cold weather is harder on the oil.    Switch to a 20W/60 motorcycle oil in the 100F+ summer & change every 5000 miles.    Mild weather like San Francisco, use 20W/40 motorcycle oil with a NOACK of 2.7%.         There is now a new 20W/50 “diesel” oil with a 3.7% NOACK.     These are impressive oils that far exceed Mercedes official factory oil.    New oils are coming out all the time, & I’m not afraid to switch when a better oil comes on the market.
Run DPF fuel cleaner in every tank of fuel.   BG 245 is a excellent fuel system cleaner.
Keep the AdBlue tank close to full.  In subzero weather, you don’t want to risk it splitting the tank.  Use a name brand AdBlue.   Mercedes has also admitted to a 100% failure rate on all the 2009 to 2015 AdBlue tanks.   There are a couple of options when it fails.
Put 2 bottles of engine oil flush in your dirty oil right before you drive in for a oil change.   It will help break up the sludge.   Liqui Moly Engine Flush is very good, but you can use other brands with no problem.     Do it on every oil change.   A quart of Marvel Mystery oil in with the new oil every oil change, will help reduce the sludge.    (I know Mercedes says not to use oil additives.    I also know about poisoning the DPF.    The engine is the most important.    Everything else is secondary.)
Get a super magnet drain plug from Dimple Magnetic Drain Plugs.   It will trap all the metal smaller than 35 microns the oil filter can’t stop.
There is a new aftermarket oil filter housing that is much bigger then the original.   It uses a big spin on diesel oil filter.     It will control the soot in the oil.   It works best on a Sprinter with the V6 diesel.   It cost $300, which is not bad for such a quality part.
Take the Belly panels off under the engine.    It needs all the air flow it can get.    There really is no other way to get rid of the crazy heat.   The cooler it runs, the less stress it puts on oil seals, plastic, rubber, & electrical parts.    If you live where it’s below zero, you may leave them on.    The panels catch oil leaks that owners don’t realize the engine is actually leaking.    On the downside, your friends are going to tell you to not park in their driveway.   Most Sprinters don’t have belly panels.
If you ever compared the oil filter from a 1980 diesel & a modern diesel, you would notice the older oil filters were twice as big.   Bigger is better.   Diesel oil picks up a lot of soot.   That’s why it turns black so fast.   Soot in oil is bad.   Change the oil filter every 2500 miles.
Only the BlueTec diesel engine has Motor Mount support arms that are filled with a special grey “heat sink” material.    (Sprinter’s don’t use this system.)    They are designed to withstand extremely high heat.   Engineers are trying to prevent the extreme engine heat from boiling the oil out of the motor mounts.    The motor mounts are hydraulic / fluid filled.    The BlueTec engine runs so hot, it melts the grey “heat sink” material that was designed to withstand extreme heat.    Grey sludge leaks out under the engine & causes a mess you won’t believe.   If the engine runs so hot it can melt this stuff, guess what it’s doing to the oil?    (“Engineered like no other car in the world.”)
Change the Air Filters every 20000 miles.
Fuel filter every 30000 miles.    Replace the rubber hoses to the filter.   Rubber flakes off old hoses & ruins the fuel pump.
Never use Bio-diesel fuel.   I don’t care what anyone says, it’s not worth the risk.    I’ve heard that Bio-diesel is unintentionally getting mixed up at stations by careless fuel delivery drivers.    Some stations don’t label the pump.   B5 is the only Bio Diesel Mercedes says you can use.   Don’t touch the stuff.   Refuel at busy stations.   When traveling, plan ahead & refuel at half a tank with zero Bio Diesel.   That way if you can’t find the right fuel, you can keep going until you do.
Mercedes has now started to recommend the EGR valve be cleaned every 40000 miles.   Burnt oil clogs it.   We found a way to really clean the EGR & the rest of the emission system.   We took the Liqui Moly kit for cleaning the DPF, & modified it.   We remove the sensor in the EGR pipe.   We made an adapter that threads into the EGR pipe & connect it to the Liqui Moly gun in their DPF cleaning tool.   We put BG 245 diesel fuel system cleaner into the gun & spray the BG 245 cleaner straight into the EGR pipe as the engine is running.   The BG 245 really cuts through the crud in the EGR system & it cleans the DPF at the same time.   The whole system is getting a serious cleaning.   This is simple, once you make up all the adapters to make it work.    (The adapters don’t have part numbers.    Old mechanics have drawers full of oddball fitting & they can find the ones that connect to the EGR & the Liquid Moly flushing tool.)
When you go in for service, ask the shop to do a manual regeneration of the DPF.    The Mercedes-Benz tester can force the system to clean itself.
Drive it like you stole it.   It helps keep the DPF clean.   (This is also in the 2018 BlueTec owners manual.)
Owners who drive long distances at high speeds, will have the fewest problems.

I’m getting reports of Sprinter frames cracking at the rear suspension.
Dealers are telling owners the vehicle can’t be fixed & Mercedes won’t pay for it.    Some dealers have dozens of cracked Sprinters.    I don’t know what years or if they were used for towing.    It’s worth asking your local mechanic to check for stress cracks in the rear.