Breese Berkowitz of Walnut Creek bought a new 2015 Passat TDI on Sept. 12 to replace an aging Toyota Prius hybrid. Her family’s other car is a plug-in Prius, and she wanted something environmentally friendly but not another plug-in because she needed a longer range. Volkswagen had been advertising its “clean diesel” technology and Berkowitz thought the Passat — the “Eco-friendly Car of the Year,” according to Cars.com — offered great gas mileage without sacrificing performance. On Sept. 18, she and everyone learned it was a fraud, that Volkswagen had installed so-called defeat devices on 11 million Volkswagen and Audi...