I believe it gives them better fuel mileage, better performance, and more power from a given design, essentially by skipping the energy cost of rectifying the N

I believe it gives them better fuel mileage, better performance, and more power from a given design, essentially by skipping the energy cost of rectifying the NOx emissions. [0] The defeat device lets them pass regulatory muster by using lower-performing but cleaner tuning when under test, then the engine uses performance-optimized tuning instead under ordinary driving conditions. [0] https://www.cbsnews.com/news/vw-just-the-latest-in-long-history-of-cheating-car-companies/ https://www.cbsnews.com/news/vw-just-the-latest-in-long-hist...