What does Das Kartell involve? More than 200 staffers from the German automakers have met since the 1990s in 60 working groups on technical issues, such as curbing emissions and brake systems.

The cartel allegations notably focus on the AdBlue selective catalytic reduction system, which uses urea to clean up nitrogen-oxide emissions and needs a 5-gallon (19-L) tank to work. Reports in German national news magazine Der Spiegel contained allegations that the companies agreed to use maximum 2.1-gallon (8-L) tanks allowing more trunk room but rendering AdBlue ineffective.

Daimler and VW blew the whistle on the cartel in July and the EC launched an investigation.

“The Commission can confirm that Daimler and VW are cooperating with the Commission under its leniency program,” an EU spokesperson tells WardsAuto, adding the program “is an effective method for the Commission to uncover and sanction anticompetitive agreements between companies.”

The cartel probe has prompted sharp criticism of the German auto sector by environmentalists. Greg Archer, clean-vehicles director at the European think-tank Transport & Environment, says: “Following the Dieselgate scandal it is illustrative of an industry that views itself above the law with an unhealthy influence over the design of European regulations; and close relationships with governments that are desperate to preserve domestic jobs in manufacturing.”

The German automotive-industry association VDA has been contrite. It has said the “allegations must be pursued consistently,” adding the auto industry for its part “have to cooperate with the authorities without restriction and provide full information.”

The VDA says that for it and its 600-plus members, “illegal agreements, as well as surfing in legal gray areas, are unacceptable.”

Meanwhile, the inquiries continue. On Oct. 16 the commission and the Bundeskartellamt, Germany’s antitrust body, swooped in on BMW’s premises to look for evidence of anticompetitive behavior, both on paper and electronically. Oct. 23 was Audi, Daimler and VW’s turn.

Both times the EC issued statements announcing the raids, but not which companies were involved – although the companies themselves subsequently disclosed their involvement.

The EC said the inspections related to “concerns that several German car manufacturers may have violated EU antitrust rules that prohibit cartels and restrictive business practices.”  But, it stressed: “The fact that the Commission carries out inspections does not mean that the inspected companies are guilty of anticompetitive behavior, nor does it prejudge the outcome of the investigation itself.”

Its caution reflects how the probe could take over a year as the EC has no legal deadline to complete antitrust inquiries.