Volkswagen AG appointed Porsche brand chief Matthias Mueller as chief executive officer as the German carmaker reels from the biggest crisis in its history.

The supervisory board, which met for seven hours on Friday, named four-decade company veteran Mueller to replace Martin Winterkorn, who quit Wednesday as the diesel cheating scandal widened and countries around the globe announced investigations. Mueller will lead Porsche as well until a successor is found.

“My most urgent task is to win back trust for the Volkswagen Group - by leaving no stone unturned and with maximum transparency, as well as drawing the right conclusions from the current situation, Mueller said in a statement. “Under my leadership, Volkswagen will do everything it can to develop and implement the most stringent compliance and governance standards in our industry.”

The 62-year-old Porsche chief takes charge a week after VW was found to have cheated on diesel-emission tests in the U.S. beginning in 2009, triggering billions in potential fines and a U.S. criminal investigation. The crisis wiped about 20 billion euros ($22.4 billion) off VW’s market value this week, and the company estimates irregularities on diesel-emission readings extend to 11 million vehicles around the world.

Mueller was already touted as a potential CEO successor when former Chairman Ferdinand Piech failed in a bid to oust Winterkorn in April. He’s run the maker of the 911 sports car since October 2010. Mueller, who studied information technology and joined the Audi division as a toolmaking apprentice in the early 1970s, is the first non-engineer to run VW since 1992, when Carl Hahn retired from the post. Hahn studied economics.

Mueller -- who has a cool, cosmopolitan demeanor -- boosted Porsche profit 62 percent over four years. Deliveries are on track to surpass 200,000 vehicles for the first time in 2015, with the addition of new models such as the Macan compact SUV.

“We know and value Matthias Mueller for his determination and decisiveness,”said Bernd Osterloh, VW’s labor leader. “He does not work on his own rather he is a team player. That is what Volkswagen needs now.”

VW shares closed down 4.85 euros on Friday, bringing their loss for the week to 34 percent.