Another new day, another opportunity for the ramifications of VW’s efficiency cheating scandal to bounce around the world on social media and, increasingly, in the pages of the tabloids.

A crafty way to get around the emissions tests on half a million US-market diesel cars is worthy of a mention, it seems; the confession that the crisis could in fact affect 11 million vehicles worldwide has made the people’s car the people’s news.

In so doing, it has muddied the waters - to the point where it’s worth clarifying exactly which test VW has admitted to twisting. For this not a question of fuel economy or CO2 figures; it is about the potentially more harmful NOx particulates that are causing so many issues in traffic-heavy cities worldwide. The mainstream media - keen to tap into the pent-up frustration about the official fuel economy figures - has been quick to ask questions on the shortfall between those numbers and what we can all achieve in the real world. It’s an issue, no doubt - and one that our sister title What Car? has tried to address with its True MPG on-the-road tests. But it’s not what’s at stake here.

If anything, NOx has the potential to become a bigger issue than CO2 has ever managed to be. Sure, the big manufacturers bleated when they were set aggressive fleet average targets - and Winterkorn himself spoke out on the matter at last autumn’s Paris motor show, revealing that every 1g/km of CO2 emissions reduction costs VW 100 million euros. But the industry continues to hit and surpass those CO2 goals - allowing millions of motorists to save on taxes and claim the environmental high ground, often by choosing diesels.

All the while, though, NOx targets have been casting an ever-longer shadow over that buyer trend - and in the space of the past 48 hours, the gloom has become darker still. If nothing else, and fairly or not, the credentials of even the latest 'clean' diesels on NOx emissions have been shaken to their core.

Small wonder that respected industry analysts are saying that the VW case - still an isolated issue for a single manufacturer until any evidence suggests otherwise - could accelerate even tighter regulations that are even harder to hit (legitimately). This, in turn, could kill diesel sales in the US before they’ve really started, and dramatically alter the near-even market split between diesels and petrols in Europe. These developments - and the resulting prohibitively high costs of diesel cars in general - are what will drive the change, though, rather than a shortfall in real-world fuel economy.

As for VW and Winterkorn, today will be another day of intense pressure for clarity and information and, in the case of the CEO, further speculation on how long he can stay in the top job. A man with an engineering background, Winterkorn has made his career not through glossy presentation (quite the opposite, in fact, if yesterday’s wooden, vaguely arrogant video address was anything to go by) but by shrewd planning and mechanical nous.

Whether either of those strengths can get him safely beyond two days that have seen VW’s stock value drop by 35% remains to be seen. By comparison, his recent (successful) power struggle with Ferdinand Piech looks like child’s play.

Read more on the Volkswagen emissions scandal:

How the Volkswagen story unfolded

How VW's 'defeat device' works

VW board anticipates more top-line casualties

European cars are affected, says German minister

PSA Peugeot Citroën leads calls for tougher emissions test procedures

Your key questions answered

BMW - why the X5 complied with independent US emissions test

Blog - The VW Scandal and the growing dangers of its ripple effect

Blog - VW's scandal has put the entire motor industry under pressure

Blog - Winterkorn pays a high price

Blog - the emissions scandal could sink Volkswagen's US ambitions

Blog - are we about to see the death of diesel?

Blog - VW's US boss faces the music

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