A researcher from Leeds University says that at least four other automakers’ cars are polluting above the legal limits for Europe, including Ford, BMW, Mazda and Mercedes-Benz, the Daily Mail reported.

James Tate, a researcher and lecturer at the university measured over 300 new cars to comply with new Euro 6 diesel emissions standards. According to Tate, Mazda’s diesel engines, on average, emitted more than six times the European limit for nitrogen oxide emissions in new cars. Ford’s cars may have polluted more, but Tate said the automaker’s sample size was too small to tell.

According to the report, Tate used a roadside sniffer for testing in the UK, similar to ones used in the United States.

“This research shows that building cars so they perform well in laboratory emissions tests but emit high amounts of NOx in real urban driving is an endemic practice across the industry,” Tate said, according to the Daily Mail. “There is very little known about how the manufacturers conduct their tests because they take place behind closed doors.”



Since the scandal involving Volkswagen broke, several industry groups and research agencies have reported discrepancies with automakers’ reports of legal diesel emissions. Automakers such as BMW, Mercedes-Benz and Fiat Chrysler Automobiles have denied their cars have cheated emissions tests.

Interestingly, Tate said Volkswagen’s diesel cars weren’t the most-heinous offender.