As a result, VW could very well lose the king-of-the-hill status it obtained during the first half of this year, when it pushed past Toyota to become the world's best-selling automaker.
Even as its status in the automotive hierarchy has grown, however, VW has struggled to turn record sales into record profits. While most of the world's major makers reported gains during a generally strong second quarter, Volkswagen saw a 16 percent drop in its after-tax profit during the second quarter, to 2.73 billion euros.
That led former CEO Winterkorn to enact a number of cost-cutting steps over the past year. But one key measure meant to put the automaker on track hasn't paid off as anticipated.
Like key competitors such as Toyota and General Motors, VW has developed a handful of so-called vehicle "architectures" that can be shared by a wide range of models and brands. But instead of yielding major savings from improved economies of scale, "they are far more expensive to produce," noted Phillippi.
Another long-term challenge for Mueller will be to decide whether to continue VW's strong dependence on diesels—which, of late, had accounted for a quarter of its sales in the U.S. and nearly half in Europe.
But the automaker was already putting more and more emphasis on battery technology to meet emissions and mileage targets. At the Frankfurt Motor Show, several executives said hybrids, plug-ins and pure electric models would likely begin to replace some high-mileage diesel options.
For the moment, Mueller will have to pick up where Winterkorn left off, by sounding a strong note of contrition. He will have to put profits aside to fix the more immediate challenge—regaining the trust of both the public and regulators around the world.