It’s to bad Mercedes-Benz didn’t use Break-in oil in their BlueTec diesels.   If they had, the piston rings would have formed a perfect seal with the cylinder walls.  BlueTec diesel’s run much higher compression than earlier diesels or gas engines.  BlueTec diesel’s have abnormally high levels of fuel dilution.  Piston rings with the tightest possible sealing tension will benefit from less diesel fuel getting past the piston rings.

As the engine is running the BlueTec emission system occasionally injects extra diesel fuel to “regenerate” the DPF.    That extra diesel fuel tends to wash past the piston rings and into the crankcase oil.    The tighter the piston rings press against the cylinder walls the harder it is for diesel fuel to get past the rings.

In order to achieve a perfect seal between the piston rings and the cylinder walls, the engine should use special Break-in oil in the crankcase for the first 1,000 miles.    But Mercedes doesn’t use Break-in oil because the EPA decided years ago that they wanted to reduce waste oil going into the environment.    So engine builders stopped using Break-in oil.  It’s now up to individual owners to undertake this vital procedure.

These days BlueTec engines come with standard Mobil One 5W/30 ESP engine oil.  Mercedes tells owners they can go 20,000 miles on this oil.  But Synthetic oil has too many friction modifiers to allow the piston rings to form a perfect seal with the cylinder walls.   If you then try to extend the Break-in period from 1,000 miles to 20,000 miles it’s no wonder that engines have so much blow-by deposits on the rings keeping them from forming a good seal and allowing diesel fuel to pass into the crankcase oil.

You couldn’t come up with a worse way to Break-in a BlueTec engine.    The Mobil One 5W/30 ESP is one of the worst diesel oils on the market.   And that’s Exxon Mobil’s own opinion from an internal report that spells out this oil’s specs.    Oh boy, are those specs awful!

If you wanted to tell BlueTec owners the worst possible way to Break-in their new Diesel engine.  I suppose you could have told them to throw a bucket of gravel into the crankcase, but other than that, Mercedes-Benz chose the worst way possible!

If you follow the salesman’s advice and drive your new BlueTec diesel 20,000 miles on the factory fill of Mobil One 5W/30 ESP oil, you’ll have piston rings and cylinder walls with a less than a perfect sealing surface.  Because the BlueTec dumps extra diesel fuel into the combustion chamber for regenerating the DPF, that diesel fuel has an easy path past the piston rings and into the crankcase oil.

Often owners will call their dealer to report that the “oil over filled” warning light is on.    The Service Advisor tells them to stop by and they will suck some oil out of the crankcase.    But they don’t tell the owner it’s diesel fuel that’s flooding into the crankcase.    And sadly, before the engine is even out of warranty, it’s already deep in trouble.  It is absolutely heartbreaking knowing the engine is being so abused.

Look at all the cool stuff Master Upfitters are doing to Sprinters RVs, limousines, and executive shuttles.  Or look at contractors who outfit them for work and count on them every day for their livelihood.  It would be nice to know that employees can focus on their work and not worry about being stranded in the company Sprinter.  Who cares if it’s covered under  warranty?   Who needs the inconvenience?

I watch the advertising videos about the Sprinter RV’s and they all show the neatest cabinetry and the latest electronics.  As soon as they open the hood they spend 15 seconds talking about the fuel efficient Diesel engine and that’s the end of the conversation.  Not a single word about maintenance.

Wait until your Sprinter goes into limp home mode and you’re in the High Sierras or you have to be towed 500 miles to the nearest Mercedes-Benz dealer.  It is so easy to do some basic preventive maintenance when the engine is new and then it would be bulletproof.

But if you ask your MB dealer to help you with a proper Break-in, they will tell you it’s not necessary on modern engines.  “Break-in is outdated and a waste of money.”  When the salesman tells you, “it will go half a million miles without a problem”, don’t fall for it.

Do a proper Break-in for the first 1,000 miles and use the best oil every 5,000 miles.   See my Blog called BlueTec Diesel Oil for some oil recommendations.  Then it really will go a half a million miles.