No-no-no-no-no-no, listen to me…diesel in Latin means ‘dirty.’

In its memorable “old wives’ tales” commercials for its “clean diesel” cars, Volkswagen humorously sought to dispel outdated beliefs that diesel cars were stinky, sluggish, and dirty. Offering a fun yet green alternative to dull hybrids, the company promised the best of both worlds: sporty, driver-focused vehicles, with real-world highway fuel economy upwards of 50 mpg and low emissions. Notwithstanding brilliant advertising, were the old wives in the commercials actually correct? As with most things in the legal, regulatory, and engineering worlds, the answer is complicated. Diesel can still be a comparatively clean mobility option, but Volkswagen did the technology no favors with its subterfuge.