High court rejects most of ‘dieselgate’ claims brought by 1.6m UK car owners

The high court judge ruled that ‘not every calibration or emissions-control strategy amounts to a defeat device’. Photograph: Jinny Goodman/Alamy View image in fullscreen The high court judge ruled that ‘not every calibration or emissions-control strategy amounts to a defeat device’. Photograph: Jinny Goodman/Alamy High court rejects most of ‘dieselgate’ claims brought by 1.6m UK car owners Carmakers welcome ruling against suit claiming manufacturers including Nissan, Ford and Peugeot fitted devices to defeat emission tests Car manufacturers have welcomed a high court verdict that rejected most of the allegations in a “dieselgate” claim brought on behalf of 1.6 million UK owners of polluting cars. In her judgment, Lady Justice Cockerill said that “in the majority of instances, the court found that the relevant strategy did not constitute a prohibited defeat device” – software that enables the engine to behave differently in tests. However, she said that technology and strategies used in some Mercedes and Peugeot-Citroën cars could constitute defeat devices. Lawyers for the claimants said they were considering appealing, saying the judgment created a significant divergence between the legal position in Great Britain and much of Europe . The claimants had argued that manufacturers had engineered vehicles with technology that would reduce nitrogen oxide (NOx) emissions in tests compared with normal driving conditions. The manufacturers denied using prohibited defeat devices. The case against the manufacturers, the largest group action trial in English legal history, was heard in the high court over 15 weeks between October 2025 and March 2026. It focused on 20 vehicles sold by five manufacturers – Mercedes, Ford, Renault , Nissan and Peugeot/Citroën – from 2009, but the judgment also binds other manufacturers. The judge said: “Not every calibration or emissions-control strategy amounts to a defeat device.” Cockerill said proving intention to rig a test was necessary, adding: “It was not enough for the claimants simply to establish that the challenged strategies reduced the effectiveness of emissions-control systems outside the relevant testing conditions.” The judgment found that: “Testing, however, is difficult to interpret and none of the approaches to isolating the effect of a particular calibration on NOx was entirely satisfactory.” Her ruling also said that “if an alternative approach to the meaning of ‘defeat device’ were taken a larger number of defeat devices would be established, including devices in each of the lead manufacturers cars”. Mercedes-Benz said the court had ruled “very largely in favour” of the manufacturer but said it was considering an appeal over the vehicle deemed non-compliant. The functionality was removed from vehicles in 2015. Stellantis, the owner of Peugeot-Citroën, said it was considering an appeal over the upheld allegations. Nissan said it had always maintained that the technologies in its vehicles do not constitut