We all know by now that Volkswagen’s “Clean Diesel” vehicles were anything but, and that the carmaker deliberately used so-called “defeat devices” to cheat on emissions tests. Now, in an effort to get compensation for people who purchased one of these dirty diesels, the Federal Trade Commission has sued VW, accusing the company of deceptive advertising.

In a complaint [PDF] filed this morning in a federal court in California, the FTC accuse Volkswagen Group of America of violating the FTC Act’s prohibition against “unfair or deceptive acts or practices in or affecting commerce.”

Between 2008 and 2015, VW advertised these cars as “clean diesel” alternatives that had the high mileage of a diesel without all those pesky emissions. The ads and marketing for the vehicles claimed to reduce the release of nitrogen oxides (NOx) by 90% — “fewer NOx emissions than comparable gasoline engines,” claimed the company at one point.

VW and Audi clean diesel ads exhorted environmentally conscious drivers to “Do Your Part,” and reassured consumers that “Diesel. It’s no longer a dirty word.”

The carmaker produced a video featuring a “coffee filter test” comparing new Volkswagen Touareg diesel with a “traditional diesel” vehicle by placing white coffee filters on each car’s tailpipe. After 10 minutes, the filters were compared, with the Touareg filter still clean and white, while the other filter now had a black stain.

These cars supposedly met “the strictest EPA standards in the U.S.” and were compliant with emissions standards in all 50 states.

VW sold some 550,000 clean diesel vehicles in that seven-year span, becoming the country’s biggest seller of light-diesel cars.

But as was revealed last year, the cars weren’t just failing to live up to these claims; VW had been using technology to cheat on emissions tests.

When the clean diesels were on the road, they would not use their full emission-controlling systems, meaning significantly higher levels of toxins were being released — upwards of 4,000% above the legal limit of NOx, according to the complaint.

But when those same cars were put through official emissions testing, the car knew to turn on all of those systems in order to get a clean bill of health.

The specific vehicles included in the complaint are the model-year 2009 through 2015 Volkswagen TDI diesel versions of VW’s Jetta, Passat, and Touareg, along with all TDI Audi models.

“For years Volkswagen’s ads touted the company’s ‘Clean Diesel’ cars even though it now appears Volkswagen rigged the cars with devices designed to defeat emissions tests,” said FTC Chairwoman Edith Ramirez in a statement. “Our lawsuit seeks compensation for the consumers who bought affected cars based on Volkswagen’s deceptive and unfair practices.”

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