 i have a 2013 E350 BlueTech Sedan.   Has been driving this car since new,  Vehicle has been serviced regularly at the Mercedes Dealers.  At 52000 miles, Tail pipe began to blow smoke.  Took it to the Mercedes Dealer at El Cajon, CA   First diagnostic, Nox sensors failure.  All 3 Not sensors replaced.  Problem still exists, so AdBlue Injection valve was replaced, and then AdBlue tank was replaced.  How is it possible that 5 components failed at the same time, at 52000 miles.  The first 4 items are not covered by warranty.  AdBlue tank was covered by Mercedes.  They call it "Good Will" although tank is warrant for 7 years or 70,000 miles in the book.  Is this the case of "trial & error" method to diagnose the problem, or are these components so  unreliable?  Replacement of the first 4 items - $2800.  Does any one have this problem.  Mercedes called me after I returned the survey.  I gave Royce (MB) my feedback.  Good conversation but I have not heard what their internal investigation reveals, or this is a case of just chit chat.  Should I be concerned about what the next breakdown of the emission control system.  Does anybody has this problem with the BlueTech emission system?UpdateAt 53000+ miles, tail pipe smoked again, and no power when going uphill between Riverside and San Diego on I 15.  Dealer replaced catalytic converter and mufflers under warranty.  At 54000+ mile, smoke was detected under the car.  Problem - oil pan gasket was leaking.  Oil pan an gasket replaced at my cost.  It is so unreliable that I would drive this car within the distance covered by the AAA member towing allowance.  This car has gone back to dealer 3 times between 52000 and 54000 miles Resale for this car tanked.  So I will keep this car and keep the public know the maintenance cost in the future.   Really bad for Mercedes Brand.