The oil in a BlueTec diesel is much more complicated than the oil in a gas engine.  When the DPF fills with soot from the exhaust it needs to regenerate every so often to burn off the soot.  All of the extra heat and fuel dilution in a BlueTec diesel causes the engine to burn oil.  That’s why the NOACK Volatility and the oil viscosity are so important.  A low NOACK Value means the oil won’t vaporize so easy and is less likely to end up in the DPF.   In a hot running BlueTec diesel, high viscosity oil is needed for high fuel accretion and for the extreme heat.  As diesel fuel washes past the piston rings during DPF regeneration the diesel fuel thins the oil.

When the oil has a high NOACK Value oil vapor is also building up in the DPF.  Now the DPF is not just trapping the soot, it’s trapping the burnt oil vapor.  Better oil with a low NOACK Value will help as will 5,000 mile oil changes.  Another thing that helps clear the soot and oil out of the DPF is full throttle acceleration that increases the exhaust flow.  Kick it into passing gear as often as possible and it will reduce the number of DPF regenerations and fuel accretion.

When the BlueTec diesel came out in 2007, Mercedes recommended Mobil One 5W/30 ESP.  They still recommend it today.  It’s the oil that comes in a new OM642 diesel.  In the early years no one suspected there was anything wrong with the oil.  After a few years, I noticed my customers were having a lot of oil related problems. The engine ran so hot it was vaporizing the oil.  At that time Mobil didn’t publish a Product Data Sheet with any substantive information about the oil.  It was obvious the oil couldn’t handle the extreme heat in this engine.  At the time the EPA also created a lot of confusion about the diesel oil specs.  About this same time I went to a SEMA conference in Las Vegas.  It’s the largest auto trade show in the world.  While I was there I spoke with some Petroleum Engineers from several oil companies.  They explained the EPA diesel oil issues.  They suggested premium Motorcycle oils with certain additive packages.  They explained the oil regulations for Motorcycle oils were exempt from the EPA rules.  Oil companies were free to make Motorcycle oil with all the best additives.  Motorcycle oils would be better for the extreme heat and fuel dilution in a BlueTec diesel.  That’s why I used Motorcycle oils for a while.  Today there are a number of oil companies who have finally come out with diesel oils for the new engines.  It is still hard to find a diesel oil that does all the things needed for a BlueTec.  There are a few that score better than the others.  How does the factory recommended Mobil One 5W/30 ESP stack up against other diesel oils?  At this point I need to tell you this is my opinion.  I don’t have any affiliation with Mercedes-Benz or Exxon Mobil.

Mercedes has now put this disclaimer in the 2019 Sprinter Owners Manual.
{{The containers of the various engine oils are marked with the ACEA (Association of European Automotive Manufacturers) and/or API (America Petroleum Institute) classifications. Only use approved engine oils that correspond to the MB Specifications for operating fluids and the prescribed ACEA and/or API classifications named below. Engine oils of other grades are not permissible and can result in the loss of the New Vehicle Limited Warranty. The use of other engine oils not approved for diesel engines can damage the diesel particulate filter (DPF).}}
I’m sure the average owner knows exactly what Mercedes is talking about.  But for those few people who don’t know what this means I will explain.  The ACEA and API are independent oil testing and approval agencies that are funded by the oil industry.  They verify the advertising claims made by oil companies.  They are also affiliated with the government environmental agencies in Europe and America.  Engine oil is a major part of the emission system.  These legalistic disclaimers are to appease the government.  The ACEA and API rate oil for every type of engine.  They have a system that scores the oil for the type of engine and emission system it was designed for.  In this disclaimer Mercedes is telling owners they only approve oil for their BlueTec diesel that has the appropriate ACEA or API classification on the oil bottle.  That sounds simple enough.  What’s the correct classification?  Mercedes doesn’t tell owners what the classification should be, they expect owners to research this on the ACEA and API websites.  Nobody’s going to do that.  They will just trust Mercedes.  Oil is oil, they’re all the same.  Wrong!  I’ll save you the trouble of looking it up.  For a Mercedes-Benz BlueTec Turbocharged diesel, the ACEA classification should be “E9” or “C5”.  (E9 is heavy duty Diesel engines.  C5 is for passenger car Diesel engines.  They are virtually identical.)  The API classification is “CK-4”.  These are the highest approval ratings a diesel oil can have.  However, it does not mean every oil that has this approval has the same quality.  It simply means the oil is in the proper category.  To find the best BlueTec diesel oil you have to look at the Product Data Sheets to see how the oils score on the individual test.  I assume you know all of their advertising claims are BS.

So how does the Mobil One ESP rate?  Mobil One ESP has the ACEA “C2 and C3” approval.  The ACEA approves Mobil One ESP for light duty non-turbocharged diesels.  In other words, it is NOT approved for a Turbocharged BlueTec diesel.  The API gives Mobil One ESP the “SN” approval.  “SN” is the approval for gas engines.  Wait a second… I though this was a Diesel engine?  This can’t be true.  This is Mercedes-Benz and Mobil One we’re talking about.  They don’t make mistakes like this.  You’re right, it’s not a mistake.  If you look at a bottle of Mobil One ESP or the Mercedes-Benz branded 5W/30 oil, you will NOT find the ACEA or API approval on the label.  The disclaimer says one of these approvals must be on the container.  Where is it?  In plain English, the oil in the bottle is not for a BlueTec diesel.  This oil does not meet Mercedes own standards.  Maybe this finally explains why these engines have so much trouble with oil sludge and emission system failures.  It ain’t the right oil for this engine!  The Mercedes-Benz approval you see on the label “MB229.52”, is not the same as the ACEA or API.  Mercedes and other manufactures came up with their own rating system so they could get part of the profit from oil sales.  If you ask Mercedes what their approval test consist of, they refuse to answer.  But lets keep this simple.  Go to your dealer and ask them to show you the ACEA or API approval on the diesel oil bottle they recommend?  If it’s not there, the oil is not approved.  Why does Mercedes-Benz use an oil that’s not approved for a BlueTec diesel?  Their disclaimer says: The use of other engine oils not approved for diesel engines can damage the diesel particulate filter (DPF).  So is Mercedes going to pay for all the damaged DPF?  Does this mean Mercedes is going to pay for all the ruined diesel engines of customers who trusted them?  It really is very simple.  Mercedes says the ACEA or API rating must be on the oil.  It isn’t.  Mercedes says non approved oil will damage the engine.  They are correct and it did.  I would say Mercedes owes a lot of owners a lot of money.  I wonder what Mercedes is going to do when FedEx and Amazon figures this out?  All you people who bought a new BlueTec Sprinter today…. you do realize the oil in your engine is not approved for your engine?

NOACK Volatility is the oil test for extreme heat.  When oil gets hot it gives off steam.  It’s this steam or oil vapor that gets sucked back into the turbocharger.  The very best diesel oil I’ve found has a NOACK Volatility of 3.7%.  Lower is better.  The Mobil One ESP has a NOACK Volatility of 9%, but because it’s not a diesel oil, after 3 hours the NOACK Value goes to 24%.  Exxon Mobil admits it in one of their internal documents.  Because Mobil One ESP is not a diesel oil, it doesn’t handle the soot load very well.  The soot causes the Timing Chain to stretch.  This is why Mercedes has so much trouble with Timing Chains.  If you used an actual diesel oil designed for soot, the Timing Chains would last the life of the vehicle.  

Here’s another interesting new addition to the 2019 Sprinter owners manual:
{{The prescribed service interval is based on normal vehicle use. Maintenance work will need to be performed more often than prescribed if the vehicle is operated under arduous conditions or increased loads.

Examples of arduous operating conditions:
–  regular city driving with frequent intermediate stops
–  mainly short-distance driving
–  frequent operation in mountainous terrain or on poor road surfaces
–  when the engine is often left idling for long periods
–  operation in particularly dusty conditions and/or if air-recirculation mode is frequently used

In these or similar operating conditions, have the interior air filter, engine air cleaner, engine oil and oil filter etc. changed more frequently. If the vehicle is subjected to higher loads, the tires must be checked more frequently. Further information can be obtained at a qualified specialist workshop.}}
This also explains a lot of things.  Basically Mercedes is trying to find a way to tell owners they need to change their oil more often.  For years Mercedes made a big deal of telling owners they could go 20,000 miles between oil changes.  Even in this disclaimer they say the prescribed service interval (20,000 miles) is based on “normal” use.  Frankly, anyone who believed that deserves what they got.  But there are a lot of people who truly don’t know anything about mechanical things.  If Mercedes says the engine can go 20,000 miles on the oil change, they must know what they are talking about.  Even Mercedes couldn’t keep telling people this with a straight face.  So they put this disclaimer in the back of the Owners Manual.  Mercedes considers regular city driving to be arduous driving conditions.  I’m confused.  I thought “regular” and “normal” were kind of the same thing.  I thought arduous driving conditions were the Baja 1000. Or the Dakar Rally.  How about the Erzburg Rodeo.  Now we’re talking “arduous”.  Driving to Starbucks is not arduous.  But Mercedes thinks it is, so that’s all that counts.  So you’re driving around Starbucks looking for a parking place.  Mercedes says this is arduous and the oil needs to be changed more often.  Great, let’s do it.  When do we change the oil?  19,000 miles?  18,000 miles?  

You really should read the Owners Manual.  Mercedes threw this little warning in there.  {{If the vehicle is predominantly used for short-distance driving, this could lead to a malfunction in the automatic cleaning function for the diesel particle filter.  As a result, fuel may accumulate in the engine oil and cause engine failure.}}
Engine failure!  Now you have my attention.  What am I suppose to do?  I think they’re saying fuel accretion will cause engine failure.  I guess they want you to use an oil that’s designed for fuel accretion???  I think they’re just trying to scare you.  Don’t worry about it.

Mercedes tossed this one in just for good measure.  {{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.}}
They sure have a thing for fuel accretion.  Now they’re “urgently” recommending regular oil changes with an approved engine oil.  I assume that doesn’t mean Mobil One ESP.  They keep yakking about the oil changes.  Now they urgently want you to change the oil at 20,000 miles? We heard you.  It will take most people 2 years to go 20,000 miles.  I guess they’re saying you’ll be in big trouble if you go 21,000 miles on the oil.

If you want help finding the right oil or getting your engine back into good health, I can show you how and what to do.  If you’re a loyal Mobil One customer, I can even show you the Mobil One that actually has the correct ACEA and API approvals for your engine.  It’s still not my first choice, but it’s way better then the Mobil One Mercedes is using.  Whatever you decide, I’ll make sure the oil you use will comply with the warranty regulations.
Even the very best oils can’t hold up against a Turbo that reaches 1600F when it regenerates the DPF.  There are a number of things to address the hot oil vapor that will finally clog the EGR and intake system.  A Catch Tank is critical for this engine.  There are also known problems that Mercedes admits in Service Bulletins.  They have updated parts.  When you get regeneration fault codes, there are several things that automatically need to be done.  The same with low boost fault codes.  Each year has its own problems that you have to automatically address.  You won’t save money by ignoring them and hoping it won’t happen to you.  (916.715.0665)