A UK High Court judge on 10 July 2026 rejected the majority of allegations in a mass dieselgate class action brought on behalf of approximately 1.6 million UK car owners, delivering a broadly favourable ruling for Mercedes-Benz Group AG (MBG.DE), Ford Motor Co. (F), Renault SA (RNO.PA), Nissan Motor Co. (7201.T) and Stellantis NV (STLA), which owns the Peugeot and Citroen brands. The ruling followed a trial — which began in October — focused on 20 sample vehicles produced by five manufacturers. Judge Sara Cockerill said she had 'rejected most of the principal allegations advanced against the manufacturers whose vehicles were examined at trial' [Source: Reuters], and that 'in the majority of instances, the court found that the relevant strategy did not constitute a prohibited defeat device' [Source: The Guardian].

The judgment was not without adverse findings. Cockerill said some had been made, including a finding that a 'split mode' of combustion strategy in a Citroen vehicle amounted to a prohibited defeat device [Source: Reuters]. Mercedes-Benz welcomed that the court had ruled 'very largely in favour' of the brand [Source: GB News]. Friday's ruling, while relating to test cases involving the five named carmakers, will also be binding on a further approximately 800,000 similar claims against other manufacturers, making it one of the most consequential legal determinations yet in the UK's extended diesel emissions litigation.

The case represents the most significant hearing yet in 13 groups of lawsuits brought by around 1.6 million claimants. The UK government reiterated its position on the underlying conduct: a Department for Transport spokesperson said 'Defeat devices are illegal, misleading for drivers and can have negative health impacts on the public,' adding that its investigation into the issue continues [Source: GB News].

The ruling follows a prior UK settlement in the original dieselgate scandal, in which Volkswagen settled a High Court claim worth £193 million covering more than 90,000 drivers in England and Wales, with VW having admitted that 11 million vehicles worldwide were affected. The current proceedings represent a broader second wave of UK litigation targeting additional manufacturers across a much larger claimant base.

Sources: Bloomberg, BBC, The Guardian, Reuters, GB News