UK High Court largely clears Mercedes, Renault and Ford in 1.6m-driver diesel emissions class action
A 369-page ruling by Lady Justice Cockerill found that most emissions-control strategies in 20 sample vehicles did not amount to prohibited defeat devices, though one Mercedes strategy and some Peugeot-Citroën units were flagged.
The scope of the lawsuit
Around 1.6 million motorists in England and Wales sued more than a dozen manufacturers, claiming diesel vehicles built from 2009 onwards contained prohibited defeat devices (PDDs) that misled buyers about real-world emissions. The ten-week trial, which concluded in March 2026, examined 20 sample vehicles drawn from five manufacturers: Mercedes-Benz, Renault, Nissan, Ford, and Peugeot-Citroen. Claimants argued the cars sensed test conditions and altered harmful emissions (particularly nitrogen oxides) to stay within regulatory limits.
What the court decided
In a 369-page ruling handed down on 10 July 2026, Lady Justice Cockerill rejected most of the principal allegations. The judgement stated that not every calibration or emissions-control strategy qualified as a defeat device.
For a defeat device to be found, there needs to be an intention to cause the emissions control system to operate differently when it senses it is being tested.
The court found that establishing reduced effectiveness of emissions controls outside testing conditions was insufficient on its own. The ruling covered Mercedes-Benz, Renault, Peugeot-Citroën, Nissan and Ford, all of whom denied the accusations.
The two exceptions
The judgement did single out two sets of strategies. One was a device fitted in Mercedes vehicles that the manufacturer removed via a software update in 2015; the court deemed it non-compliant prior to that update. Another exception involved emission-control strategies used in some Peugeot-Citroën vehicles. Outside those findings, the bulk of the claims were dismissed.
- Volkswagen admits equipping 11 million engines with emissions-cheating software, triggering the global Dieselgate scandal.
- Multiple civil and criminal proceedings are launched worldwide against several carmakers, including the UK class action.
- Ten-week High Court trial concludes in London, examining 20 sample vehicles from five manufacturers.
- Lady Justice Cockerill hands down 369-page ruling rejecting most allegations; Mercedes and Peugeot-Citroën strategies partially flagged.
- Mercedes-Benz states it is actively considering an appeal against the finding on its pre-2015 device.
Manufacturers react
Mercedes-Benz welcomed the overall outcome but pushed back on the finding concerning its pre-2015 device. In a statement, the German carmaker said it disagreed with the court's assessment and was weighing all options.
In our view, the emission control software functionalities are justifiable on both technical and legal grounds. We are actively considering all of our available options, including a potential appeal.
Peugeot-Citroën had yet to comment by the time the ruling was published. Renault, Nissan and Ford did not issue immediate public statements.
A fragment of the wider Dieselgate legacy
The UK case is one of many civil and criminal proceedings spun off from the global scandal that erupted in September 2015, when Volkswagen admitted equipping up to 11 million engines worldwide with software capable of manipulating emissions levels. Today's ruling deals only with the five manufacturers whose sample vehicles were examined at trial, though the broader litigation involves more than a dozen car companies. Solicitors for the claimants noted that Lady Justice Cockerill's phrasing left the door ajar for further argument, but the summary of the decision made clear that the court rejected most of the final allegations advanced against the manufacturers.
