BlueTEC is Daimler AG's marketing name for engines equipped with advanced NOx reducing technology for vehicle emissions control in diesel-powered vehicles. The technology in BlueTec vehicles includes a selective catalytic reduction (SCR) system that uses diesel exhaust fluid, and a system of NOx adsorbers the automaker calls DeNOx, which uses an oxidizing catalytic converter and diesel particulate filter combined with other NOx reducing systems.

The BlueTEC was on the Ward's 10 Best Engines list for 2007 and 2008.[1][2]

In February 2016, Mercedes-Benz, Daimler AG, Bosch LLC and Bosch GmbH were sued by private plaintiffs alleging BlueTec violates standards in a manner similar to the Volkswagen emissions scandal.[3] On December 6, 2016 U.S. District Judge Jose L. Linares dismissed the lawsuit without prejudice, finding the plaintiffs had alleged no standing.[4] The case was reinstated after Plaintiffs amended the complaint, and the litigation is ongoing.


Daimler introduced BlueTEC in the Mercedes E-Class (using the DeNOx system) and GL-Class (using SCR) at the 2006 North American International Auto Show. At that time, these BlueTEC vehicles were 45- and 50-state legal, respectively, in the United States (a 45-state vehicle does not meet the more stringent California emission standards that have also been adopted by four other states).

Daimler AG has entered into an agreement with Volkswagen and Audi to share BlueTEC technology with them in order to increase the Diesel passenger-vehicle market in the United States.[5][6] VW introduced the Jetta Clean TDI, the Tiguan concept, and the Touareg BlueTDI as part of the BlueTec licensing program. The Jetta and the Tiguan use NOx adsorbers, while the Touareg uses a Selective Catalytic Reduction catalytic converter.[citation needed]

In August 2007 VW Group announced that cooperation on BlueTEC with Daimler AG would end. The reasoning for this change is due to the recognition of the VW TDI branding. VW did not want to use a competitor's branding for a product they would introduce into the market.[7][8] VW developed their own system, but it failed and they re-programmed the engine control to show false values during pollution tests.[9][10][11]

By 2010 a BlueTEC version of the Mercedes Sprinter was released. The BlueTEC systems allowed the elimination of much of the EGR in that vehicle's engine, which as a result gives 188 horsepower (140 kilowatts) compared to the non-BlueTec engine's 154 horsepower (115 kilowatts).[12]


The BlueTEC system was created because diesel engines, while more fuel efficient than gasoline engines, operate at lean air-fuel ratios, preventing them from implementing the highly-efficient three-way catalysts employed for NO
conversion in gasoline engines, which operate at stoichiometric air-fuel ratios. Limiting NO
by use of engine controls alone is possible, but requires a significant penalty to fuel economy. Tier 2 regulations in the US are 0.07 grams per mile of NOx, which is ⅛ of the 0.40 limit in the European Union.[13][citation needed]


The emissions system works in a series of steps:

  1. A diesel oxidation catalyst reduces the amounts of carbon monoxide (CO) and hydrocarbons (HC) released from the exhaust.
  2. A DeNOx catalytic converter begins a preliminary removal of oxides of nitrogen.
  3. A particulate filter traps and stores soot particles, burning them off when the filter gets full.
  4. If the above are not sufficient to meet the prevailing emissions regulations, a Selective Catalytic Reduction (SCR) catalytic converter will convert the remaining nitrogen oxides to nitrogen and water; so-called diesel exhaust fluid (solution of urea and water) is injected into the exhaust gas stream to enable the conversion. In order to prevent vehicles from breaking emissions regulations, the engine may go into a limp-home-mode if the DEF tank is depleted; drivers are instructed to keep the tank refilled as necessary. Some commercial vehicles are equipped with a request or inhibit switch which allows the DEF injection to be "postponed" as it can reduce power output and increase temperatures temporarily; if the vehicle is climbing a grade, for example, it may be necessary to delay the cycle.

Emissions defeat device allegationsEdit

The Netherlands' official automobile inspector TNO, on behalf of the Dutch Minister of the Environment, conducted an on-road test of a C-Class Mercedes C220 CDi BlueTec diesel and determined it emitted more than 40 times the amount of cancer-causing NO
than in the lab test.[14] The tests were done at temperatures below 10 degrees Celsius (50 °F). Mercedes says it is permissible for the BlueTec engine to emit 40 times more NO
when the temperature is less than 10 °C (50 °F).[15]

As of April 22, 2016, Mercedes-Benz USA disclosed it is under investigation by the Department of Justice for potential discrepancies over its diesel emissions certifications, according to a Daimler statement. The DOJ effectively told MBUSA to begin an internal investigation "to review its certification and admissions process related to exhaust emissions in the United States," Daimler said. The company "has agreed to cooperate fully with the DOJ."[16]

In Feb 2018, German newspaper Bild am Sonntag reported that US authorities investigating Mercedes have discovered that its vehicles are equipped with illegal software to help them pass United States' stringent emission tests. The claimed defeat devices include a "Bit 15" mode to switch off emissions after 16 miles of driving (the length of an official U.S. emissions test), and "Slipguard" which tries to directly determine if the car is being tested based on speed and acceleration profiles. Bild am Sonntag said it found emails from Daimler engineers questioning whether those functions were legal.[17][18][19]


  1. ^ "Ward's Announces 10 Best Engines Winners for 2007". Ward's AutoWorld. 2006-12-05. Archived from the original on 2009-07-22. Retrieved 2009-07-25.
  2. ^ "Ward's 10 Best Engines Winners Reflect Fuel-Economy Focus (2008)". Ward's AutoWorld. 2007-12-13. Archived from the original on 2008-08-21. Retrieved 2017-03-06.
  3. ^ Harris, Andrew M (18 February 2016). "Mercedes Faces Lawsuit Over BlueTec Clean Diesel Emissions". Bloomberg News. Retrieved 8 December 2016.
  4. ^ Teichert, Erica (6 December 2016). "U.S. judge throws out emissions fraud lawsuit against Mercedes". Reuters. Retrieved 8 December 2016.
  5. ^ "2008 VW Jetta TDi coming with BlueTec and 50 state emissions".
  6. ^ "The future demands more environmentally friendly technologies". Archived from the original on 2015-10-06.
  7. ^ "Daimler verliert Patentstreit um Abgastechnik".
  8. ^ Retrieved August 8, 2007. Missing or empty |title= (help)[dead link]
  9. ^ "Ingenieure gestehen Installation von Manipulations-Software".
  10. ^ Ewing, Jack (2015-10-04). "Volkswagen Engine-Rigging Scheme Said to Have Begun in 2008". The New York Times.
  11. ^ William Boston (5 October 2015). "Volkswagen Emissions Investigation Zeroes In on Two Engineers". WSJ.
  12. ^ "Mercedes to bring Bluetec diesel to European-market Sprinters by 2012, but we get it first!". Apr 20, 2010.
  13. ^ "Light-Duty Vehicles, Light-Duty Trucks, and Medium-Duty Passenger Vehicles:Tier 2 Exhaust Emission Standards and Implementation Schedule" (PDF). EPA-420-B-16-015. Environmental Protection Agency. March 2016.[permanent dead link]
  14. ^
  15. ^ "Mercedes-Benz: C-Klasse unter Manipulationsverdacht".
  16. ^ "Mercedes-Benz Faces Federal Investigation over Alleged Diesel Emissions Cheats". 2016-04-22.
  17. ^ "Daimler may have used software to cheat on US emissions tests".
  18. ^ "Software may have helped Daimler pass U.S. Emissions tests: Report". Reuters. 2018-02-18.
  19. ^ "Abgasskandal: US-Ermittler belasten Daimler schwer". Spiegel Online. 2018-02-18.

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