Volkswagen ordered to recall 500,000 cars due to emissions cheating (nytimes.com)

NOx emissions are tricky. They're created by high temperatures (the reaction is endothermic).

Conversely, the hotter the engine runs the more efficient it is. To a first approximation NOx is inversely related to CO2 emissions and l/km.

Previously: https://news.ycombinator.com/item?id=10240001