The recent emissions scandal at Volkswagen left the world stunned: How can such a major carmaker allow itself to downright cheat on emissions tests?

As it turns out, though other carmakers weren't caught with their pants down, many of their diesel cars also fare much better in those tests than in real life.

A new report from Guardian, based on the latest data by Emissions Analytics, shows that diesel cars made by Mercedes-Benz, Honda, Mazda and Mitsubishi emit far more nitric and nitrogen oxide (NOx) in real-life usage than they do in tests.

According to the data, Mercedes-Benz's diesel cars produce five times more NOx than permitted by the European Union's strictest Euro 6 emission standard. Honda's cars emitted between 2.6 and 6 times the official NOx levels. One Mazda diesel car produced three times the official NOx emissions, while a Mitsubishi diesel car produced 3.4 times more NOx than permitted in Euro 6.

This report is different than the Volkswagen scandal, as no evidence of illegal activity has been found. In contrast, Volkswagen cars were found to contain a "cheat device," whose specific purpose was to defeat emissions testing. The company is looking at billions in fines, and is not yet out of trouble, as U.S. regulators are currently looking into a second piece of software that also affects the company's cars' emission controls.

Still, if practically all cars (another Guardian report last week claimed a host of other carmakers emit more pollution than seen in tests) pollute the environment significantly more than manufacturers admit, something probably needs to change.

All four manufacturers responded to the report, claiming, basically, that their cars are compliant to the regulations. While that may be true, this data shows the EU might need to introduce stricter emissions testing. “The VW issue in the U.S. was purely the trigger which threw light on a slightly different problem in the EU — widespread legal over-emissions,” said Emissions Analytics CEO Nick Molden.

This isn't the first time carmakers other than VW were implicated in the emissions scandal. In September, Europe's Transportation and Environment (T&E) organization claimed cars by several European automakers, including Audi, BMW, Mercedes-Benz, and Opel, emit more pollutants in reality than in emissions tests.