BlueTEC is Mercedes-Benz Group's marketing name for engines equipped with advanced NO_x 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 DeNO_x, which uses an oxidizing catalytic converter and diesel particulate filter combined with other NO_x reducing systems.

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

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. On December 6, 2016, U.S. District Judge Jose L. Linares dismissed the lawsuit without prejudice, finding the plaintiffs had alleged no standing. The case was reinstated after Plaintiffs amended the complaint, and the litigation is ongoing. On July 12, 2021, the court granted final approval to the proposed class action settlement, which includes cash payments to previous and current owners, free retrofits to the cars' emissions systems, and extended emissions systems warranties for the affected models. A similar settlement was reached in Canada on February 2, 2022.

Daimler introduced BlueTEC in the Mercedes E-Class (using the DeNO_x 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. 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. VW developed their own system, but it failed and they re-programmed the engine control to show false values during pollution tests.

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).

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
_x conversion in gasoline engines, which operate at stoichiometric air-fuel ratios. Limiting NO
_x 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 one eighth of the 0.40 limit in the European Union.^{[citation needed]}