Large discrepancies between emissions of best and worst diesel cars

In the real-world EQUA Index test using a Portable Emissions Measurement System (PEMS), which is similar to a RDE (Real Driving Emissions) test, it was found that there is a big discrepancy between the best and the worst diesel cars regarding NOx emissions. In 2013 the cleanest 10% emitted 265 mg/km and the dirtiest 1777 mg/km (ratio 7 to 1). In 2017 the cleanest 10% achieved 32 mg/km but the dirtiest were 1020 mg/km (ratio 32 to 1). The average diesel NOx emissions however have fallen from 812 mg/km to 364 mg/km which is a 55% reduction. The cleanest diesels are getting close to the average NOx emissions from new gasoline vehicles (36 mg/km). Also first results from particle number (PN) emission testing showed that the latest diesels emit 71% fewer particles than the latest gasoline vehicles (albeit before the deployment of gasoline particulate filters on direct injection versions). The average CO2 emissions per kilometer from diesels is approximately 18% less than the gasoline.

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