VW isn't the only carmaker with a pollution problem

While Volkswagen is the only car manufacturer to have been caught outright cheating on emissions tests, a new report by The Guardian reveals that it isn't the only car company with a discrepancy in how its diesel cars fare in emissions tests versus in real life. Mercedes-Benz, Honda, Mazda, and Mitsubishi have all been found to have diesel cars that "emit significantly more pollution on the road than in regulatory tests," The Guardian reports.

Mercedes-Benz diesel cars, for example, produce five times more nitric and nitrogen oxide than is allowed per the European Union's Euro 6 emission standard, Mashable reports. Honda's diesel cars emitted NOx levels "between 2.6 and six times the official levels," The Guardian says. Mazda diesel cars emit between 1.6 and 3.6 times the test levels, and Mitsubishi diesel autos' emissions are between 1.5 and 3.4 higher.

Spokesmen from the four companies all defended the diesel cars in question and said that they had been tested in accordance with European laws. "Since real-world driving conditions do not generally reflect those in the laboratory, the consumption figures may differ from the standardized figures," a Mercedes spokesman told The Guardian.

Still, some posit that this data reveals that this is a systemic issue that permeates the entire industry. Last week, The Guardian found that Renault, Nissan, Hyundai, Citroen, Fiat, Volvo, and Jeep all produced "significantly more" NOx in real-life driving conditions than in tests.