Credit Where It's Due. Kudos to Volkswagen.

The Boys from Wolfsburg will always be associated with the diesel emissions scandal. It began when VW was caught cheating. When undergoing tailpipe testing its "clean diesel" engine proved remarkably clean. When in ordinary use, however, the engines produced legendary fuel efficiency and impressive power only at settings that generated prohibited levels of toxic nitrous oxide emissions.

VW went into full bore damage control mode. It offered to buy back the cars from disgruntled owners along with a modest settlement for damages. Owners also have the option of having their cars "fixed" - i.e. the cheating software replaced - and just take the damages.

Here's the irony. A lot of automakers produce diesel cars or trucks and most of them are also cheating, some far worse than Volkswagen. Yet, perhaps because this is now a more or less universal problem, the others haven't been prosecuted or forced to institute buybacks or recalls.

This week it became General Motors' turn for its Chevy Silverado and GMC Sierra pickups.

"This is a shocking discovery, and a really big deal because the [nitrous oxide] limits for these big trucks are four times what the limits were for the much smaller Volkswagen passenger cars and there are more of these trucks on the road," said Steve Berman.

An article in The Guardian last year reported that 97% of diesel vehicles exceeded the NOx emissions ceiling.  The exception? That would be Volkswagen.

Surprisingly, the tiny number of models that did not exceed the standard were mostly Volkswagens, the carmaker whose cheating of diesel emissions tests which emerged last year sparked the scandal. Experts said the new results show that clean diesel cars can be made but that virtually all manufacturers have failed to do so.

The EA analysis found that just one of the 201 Euro 5 diesels tested – a Skoda Octavia – did not exceed the official limit on the road. Over a quarter of the Euro 5s pumped out at least five times the official limit, including models from BMW, Range Rover, Mercedes, Nissan, Renault and Vauxhall.

Of the 62 Euro 6 models tested by EA, seven did not exceed the official limit in real-world driving: four Volkswagens, a BMW, an Audi and a Skoda. However, an Audi A8 and a Fiat 500X were found to emit more than 12 times the official limit, while a BMWX3, a Volvo S60 and a Vauxhall Zafira were among models emitting more than six times the official limit on the road.

Another report from today's Guardian warns our regulators are not making much progress.

Diesel cars that emit up to 18 times the official limit for toxic pollution when taken on to the road are still being sold, 20 months after the emissions scandal erupted and amid an ongoing air pollution crisis.

In real world conditions, the Nissan Qashqai produces 18 times more nitrogen oxides than the official lab-based test allows under EU directives, while Nissan’s Juke pumps out 16 times more NOx pollution than the limit, according to data from vehicle testing company Emissions Analytics seen by the Guardian.

Further data reveals Renault’s Mégane and Captur models both produce 16 times more NOx when on the road. Overall, the data shows that 80% of new diesels on the market in the last nine months fail to meet the official limit when on the road.

...software upgrades from manufacturers would quickly and significantly cut the emissions of many existing diesel cars: “What you can do is turn up the effectiveness of the emissions reduction technology – it’s almost like a volume knob – and that is a software change. If they turn up the volume, you have a clean car.” But apart from cars from VW, which was caught blatantly cheating, few vehicles in Europe have been recalled.