Opel's assertion follows up a similar one by French automaker Renault, which contested findings by Germany environmental lobby group DUH that said Renault's Espace minivan emitted illegal levels of toxic emissions. Renault has since denied those findings.
Automakers have been especially sensitive to allegations of emissions-cheating practices since September, when Volkswagen was found to have programmed software in many of its diesel vehicles to cheat greenhouse-gas emissions-testing systems. VW initially set aside $7.3 billion to address the issue, which involved as many as 11 million diesel vehicles worldwide. Earlier this month, it was reported that VW may take out a loan as large as $21 billion in order to deal with the fallout.
Soon after that scandal broke, European Federation for Transport and Environment said a number of other vehicle makers, including BMW, Mercedes-Benz parent Daimler and Opel may have also equipped their vehicles with similar emission-cheat software. Shortly thereafter, BMW put out a statement saying that it never programmed its cars to cheat on emissions tests. That was followed up by a similar statement from Daimler.