Mazda, Mercedes and Others Tied to Diesel Scandal—Is Testing to Blame?


In wake of Volkswagen’s aptly-named #Dieselgate scandal, four more automakers have been roped into the ongoing diesel crisis. Mazda, Mercedes-Benz, Mitsubishi, and Honda cars have all been tested and emit “significantly” more pollution on the road than in tests. But is it entirely their fault?

“The issue is a systemic one,” Nick Molden of Emissions Analytics told The Guardian. His company has been doing more real-world testing of these cars. “For NOx, [diesel] cars are on average four times over the legal limit, because of the lenient nature of the test cycle in the EU.”

Certain vehicles from Honda, for example, were tested on the road by Emissions Analytics and found to have had over 20 times the NOx limit than in previous tests. To be clear, Honda did not use any sort of defeat devices during testing, nor any of the other automakers listed.

Honda Civic Type R, Tourer and Sport 2015

Mercedes-Benz vehicles, on average, produced over 2.2 times the legal level. Honda, on average, produced over 2.6 times the legal level. Mazda, on average, produced over 1.6 times the legal level. And Mitsubishi, on average, produced over 1.5 times the legal level. You can see the trend here.

Of over 200 engines tested by the Emissions Analytics company, only five had real-world NOx levels that matched regulatory testing.

“MEPs have been fighting for years to reform EU rules on diesel emissions-testing so they reflect real-world emissions,” said Catherine Bearder, a LibDem MEP. “Yet the powerful car lobby and national governments have fiercely resisted these life-saving changes.”


European authorities are now calling for a stricter testing system in which the tests are, “Verified by an authority not paid by the car industry.” It remains to be seen if any automakers other than VW will receive citations.

There will always be an inherent flaw in a standardized industry test. Once automakers gain knowledge of the parameters of the test, there is a great incentive to tune the car to specifically pass this test. This is reminiscent of when Hyundai and Kia were forced to retract fuel economy estimates, simply because the transmission mapping was set up for better fuel economy on the EPA test than in real world driving.

Such action is nowhere nearly as egregious as Volkswagen’s actions, but to date there was no real penalty for automakers to “tune to the test.” Yes, such lax testing should become a thing of the past, but so should our expectations that automakers are acting in good faith.

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