Until recently, Volkswagen was waging a relentless campaign to portray itself as an environmental steward, its cars on the vanguard of a clean energy revolution. It promoted diesel as a low-emissions alternative to gasoline and spent $77 million this year in the American market to advertise its diesel cars, often proclaiming their greenness.

As everyone now knows, at the same time Volkswagen was waging this eco-friendly public relations offensive, engineers at the German automaker had rigged 11 million of its supposedly clean diesel engines with software that tricked emissions tests, allowing the cars to spew far more pollutants than legally allowed.

No matter how hard Volkswagen works to resolve this crisis, the episode is likely to live on in infamy as the latest and perhaps most egregious example of greenwashing.

Greenwashing, when a company tries to portray itself as more environmentally minded than it actually is, has intensified in recent decades as consumers have warmed to sustainable and organic products and services. Brands, trying to capitalize on that trend, often try to outdo one another with eco-credentials. But in the rush to be seen as green, companies often exaggerate claims, or simply make things up.