Yesterday, Volkswagen's US CEO testified before Congress about his firm's ongoing diesel emissions scandal. Although it appears that VW Group's 2L diesel engines are the only models that were designed to fool the EPA, over in Europe questions continue to be raised about other car makers and their products.

Diesel is significantly more popular in Europe, thanks to several decades of government incentives making the fuel cheaper than gasoline. However, EU regulators had until recently been far less concerned about NOx and particulate emissions than their US counterparts. Today, The Guardian reports that diesel-engined cars from Honda, Mazda, Mercedes-Benz, and Mitsubishi all emit more NOx than allowed under the current Euro 6 standards.

The tests were carried out by Emissions Analytics, which told The Guardian that the problem "is a systemic one." The company analyzed about 50 Euro 6 diesels and 150 diesels that conformed to the earlier Euro 5 standard, and found only five emitted NOx levels that matched the regulations.