German lobby accuses GM's Opel of dirty diesels

The Opel Zafira diesel is now taking fire for its emissions.

General Motors' European Opel division has found itself at the center of its own diesel scandal after DUH, Germany's environmental lobby group, claimed on Friday that automaker's Zafira MPV pollutes more than allowed under European Union laws.

Citing testes conducted by University of Applied Sciences in Bern, Switzerland, DUH says the 1.6L Zafira diesel meets Euro-6 emissions limits while testing on a two-wheel dynamometer, but fails the same test when all four wheels are attached to a rolling road. The tests found that the Zafira spewed 2 to 4 times the amount of NOx levels allowed under Euro-6 when all wheels were spinning.

The DUH said it did not have a "a technically plausible explanation” for the variation in NOx emissions, but Volkswagen recently admitted to installing cheating devices on its diesel cars that detected when the vehicle is being put through an emissions test. VW's software cleaned up a vehicle's tailpipe emissions during testing only to have the vehicle emit up to 40 times the legal limits of pollutants during normal driving.

For its part, Opel called the cheating allegations "false and unfounded.”

"The DUH's findings imply a subtle suspicion of manipulation on our behalf," an Opel spokesman told Automotive News. "We strongly deny this accusation.”

More automakers could be swept up on the wake of the VW diesel scandal as DUH says it plans to test more vehicles from other automakers.