TDIBeing an environmentalist, I hate to admit it, but I love my vehicle.

For starters, I applaud its exceptional fuel economy—an average of 37.5 miles per gallon city (45 mpg highway) in the three years I’ve owned it. This is a significant boost above the U.S. average of 23.6 mpg for their car fleet. I love the style—sleek, compact and modern without looking flashy. I’ve even come to love the little rumble of the diesel engine that signals its latent power.

Unfortunately, my dream car is built on a big, fat lie. That’s because I’m the owner of a 2012 Volkswagen Passat TDI, one of the nearly half a million VWs that had a software installed to cheat emissions testing and “pass” clean air regulations. VW sold me, and hundreds of thousands of other Americans, a vehicle whose green “clean diesel” promises were nothing short of deceiving.

When I was first searching for a new vehicle, the Prius was quickly out of the equation upon the first test drive. For me, best-in-class fuel economy was non-negotiable, but I needed more. So that made the line of (supposedly) clean diesels the next best option. Due to their higher compression ratios and more intense internal combustion, diesel engines are, on average, about 30 percent more efficient than gasoline engines at burning petroleum. But there’s a hitch. Because a diesel engine burns petroleum at a hotter temperature, it turns more nitrogen into nitrogen oxides (or NOx). Such NOx are a main ingredient in ground-level smog, the kind of air pollution that is bad for plants and people and, with persistent exposure, contributes to lung disease and other respiratory ailments that can cause an early death.

Diesel engines’ contribution to smog meant that, for decades, American regulators frowned on diesel technology, even as European governments embraced the engines, mostly because of their superior fuel economy. Then, in the mid-2000s, the major automakers—led by German firms VW and Audi—said they had developed new “clean diesel” technology that would meet the stricter U.S. air quality standards while also delivering high fuel economy and road power. I fell for the idea of this being an actual reality and happily bought it.

As we now know, it was all a scam. Engineers in Germany had programmed the software in their diesel engines to recognize when the vehicles were undergoing a smog check. The NOx-controlling technology only switched on when the engine knew that it was experiencing a set of demands unique to testing conditions. Most of the time—under normal road conditions—the cars emit up to 40 times the allowed amount of NOx.

Being a committed environmentalist, I bought the VW Passat precisely because I believed that it was an exemplary “green car”— and I was defrauded. And now I’m ticked off. Although I dislike the litigious culture here in the United States, I have decided that I will join one of the VW class action lawsuits being prepared against Volkswagen.

I loved you until I found out you were a cheat.