"Clean Diesel." That's the line Volkswagen used to market its diesel cars in the U.S. VW promised to let owners have their cake and eat it too, attracting a bit of a cult following in doing so.

In its February 2010 review of the 2009 Volkswagen Jetta TDI — the first model year for the new four-cylinder diesel in the U.S. — Car and Driver summed up this rather miraculous car well.

"VW spent ’07 and ’08 with a diesel hole in its U.S. lineup while engineers worked to meet the new rules with a heavily revised 16-valve, 2.0-liter turbo-diesel four-cylinder that came with a particulate trap and a catalyst to kill off oxides of nitrogen (NOx ). The Jetta TDI that emerged is clean enough to satisfy the emissions laws of all 50 states without resorting to urea injection, plus, it is powerful (140 horses) and quick enough (0 to 60 mph in 8.1 seconds) to satisfy us. In fact, our TDI proved to be as quick to 60 as a manual five-cylinder gas Jetta." But the real draw of the diesel Jetta has always been, and remains, its fuel economy. Over our 39,678-mile test (VW snatched back its car just before we could hit the 40,000-mile mark), our Jetta TDI consumed diesel at a rate of 38 mpg. That number has only been bettered twice by C/D long-termers: A 2000 Honda Insight returned 48 mpg over 40,000 miles, and a 1992 Honda Civic VX got 41 mpg over 35,000 miles.

This excerpt reads very differently in September 2015 than it did in February 2010. Diesels of the past were dirty and slow, and Volkswagen seemed to have amazingly solved those issues without the need for a costly and complex urea injection system.

Now, we know Volkswagen lied.

These seemingly miraculous cars used a piece of software called a "defeat device," which detected when the car was undergoing emissions testing and turned on full emissions control systems. On the road, the systems would switch off, giving the four-cylinder TDI Volkswagens their characteristically great acceleration and fuel economy.

For many, these cars were an alternative to hybrids, which achieve high fuel efficiency numbers at the expense of style and driving enjoyment. It's the reason why so many auto journalists recommended these over hybrids like the ever-popular Toyota Prius and the reason why so many owners bought.

A file picture made available on 20 September 2015 shows a VW Passat TDI Clean Diesel during the North American International Autoshow (NAIAS) in Detroit, Michigan, USA, 15 January 2013. Image: Uli Deck/dpa/Corbis

It's the reason why James Spencer, an Office Coordinator at Columbia University's Lamont-Doherty Earth Observatory, in the office of the U.S. Science Support Program, bought one. He identifies as an environmentalist, and he chose to purchase a 2015 Jetta TDI for its supposed cleanliness and excellent fuel economy.

"I bought it for a job that has a long commute so I was looking for efficiency, but the 'clean diesel' aspect was a big selling point to me because I care about the environment," he said in a phone conversation with Mashable. "If I wanted performance I would have gotten performance; I care about it being a clean-burning diesel engine."

Spencer chose the Jetta TDI over a hybrid; "It makes me question the decision I made."

Even still, it's hard for him to be 100% angry with the situation. "It's a great car, I just want the car they sold me," he said. "It's a completely different situation than if it were something that put my safety at risk. If they cheated in some sort of aspect of safety, I would be furious... Volkswagen would be completely dead to me."

"I have a hard time being outraged when that stuff is going on," referring to the recent GM ignition switch and Honda/Takata airbag recalls, in which many were killed in the affected cars.

One New England owner of a 2010 Jetta TDI, who wished to remain anonymous for this piece, is in a similar situation as Spencer.

"At the time, I could have gotten a Prius, but they missed the pickup and the zip, they were small, they felt a bit like a tin can. What I liked about my Jetta is it was easy to drive in the city and I thought 'I'm doing my thing for the environment as well,' and now it turns out that was a sham," they said.

“No one is dying, so I think it’s going to blow over. But, at the same time, among the thoughtful, careful consumers, I don’t think they’re going to win them back easily.”

A 2009 Volkswagen Jetta TDI. Image: Volkswagen

For others, the feelings of betrayal are much more strong.

Vik Chhadbra, a 2012 Jetta TDI owner and a long time Volkswagen fan, said hearing the news was "like a punch in the gut." He's owned Volkswagens since 1994, and even sold them for a number of years, but after this he said he'll "never buy" another Volkswagen.

Volkswagen attracted something of a cult following, made up of many people like Chhadbra. "With VW, it was more than just a car brand, it stood for something."

Richard McLane, a 2010 Golf TDI owner from North Carolina who bought his car for environmental reasons, isn't a Volkswagen fan like Chhadbra, but his disappointment with the deciet is similar. He said this in an email to Mashable:

"Last Friday I found out that I have been living a lie. I've been impacting the environment, making life more difficult for people with asthma, and contributing to smog more than we, as a society have deemed as acceptable. Apparently, I have been advocating for others to do the same, advocating against some of my most closely held values. There are plenty of products I use and am happy with and will talk about if someone asks me, but there are very few that I will go on about and try and sell someone on...This was one of the few, maybe the only at the consumer level, that I felt this way about."

Still, some fans don’t want to completely write Volkswagen off just yet. Fred Voglmaier, a 2010 Golf TDI Sportwagen owner in Vancouver, is one of the biggest TDI fans out there. In 1996 he started Fred’s TDI Club, a forum for Volkswagen diesel enthusiasts like himself, with nearly 20,000 active members.

When asked how he reacted upon first hearing the news, he said “It was hard to sort of take in. I still haven’t probably grasped the whole thing; I’m more of a person who wants to get all the facts. The deception part of it where it wasn’t doing what it’s supposed to do, that’s a bit hurtful.”

The forum’s post on the scandal is the fastest-growing in TDI Club’s history, with 478,441 views and 282 pages worth of replies after just one week. Voglmaier said the posters on the forum are a diverse group and the reactions to this ongoing scandal are reflective of this. For him, he’s waiting to see if and when Volkswagen does the right thing.

One of the other groups of people that loved these unusual cars was automotive journalists (including this reporter). For the same reasons many owners chose Volkswagen TDIs over competing hybrids, car reviewers loved and always recommended them to people looking for green cars that were still fun. Patrick George, Managing Editor at automotive enthusiast blog Jalopnik (and, it should be noted, a former colleague), drove the 2015 Golf TDI SportWagen at its launch event earlier this year and gave it a glowing review.

“A lot of journalists recommended this car for years. Any time someone was looking at a hybrid, it was kind of like ‘Well you know, some of the hybrids are decent, but some of them are also really boring. You should look at these too because they have great fuel economy, a ton of power, fun to drive and they’re good on emissions,’ Like the people who bought them, that’s how we all understood these cars to be.”

When asked about how he felt recommending Volkswagen diesels, he said “I feel a little bad about recommending these to people over the years, but at the same time, like the buyers themselves, we made these recommendations on the information we were given and nobody knew about this.”

George’s outlook on Diesel itself is less optimistic. In a post on Jalopnik he said;

“As emissions standards get tougher and tougher here and in Europe, the diesel’s future looks increasingly dismal. European cities are increasingly cracking down on sources of poor air quality, diesel cars and buses in particular. Many industry watchers wonder if the fuel has had its day. The French government has said they’d like to eventually phase diesel out. And here in the U.S., if a particularly ambitious, environmentally-minded lawmaker wanted to move to outlaw diesel passenger cars, VW has just given them the perfect amount of ammunition to do it.”

A man cleans a Volkswagen logo during the general meeting of car manufacturer Volkswagen in Hamburg, Germany, 19 April 2012. Image: EPA/MARCUS BRANDT/Corbis

This is an interesting group of cars to be implicated in such a scandal. Unlike the Chevrolet Cobalts at the center of GM's ignition switch recall woes, these were special cars.

Especially in the U.S., the sort of customer who bought a Volkswagen TDI made the choice to buy something different; something out of the ordinary. It was never a car that would have been purchase by accident.

Customers bought them for different reasons; Volkswagen fandom, performance, fuel efficiency and of course, the desire to be green. In talking to a number of owners, one gets the sense that these cars are, or in some cases, were loved.

To owners, Volkswagen TDIs weren't just a means of getting from Point A to Point B, they were rolling representations of their ideals. Their cars communicated their values, based on what Volkswagen claimed for them to be. This isn't a case of "your car is broken and you need to get it fixed," it's "this thing you believed in turned out to be a lie."

"People like us are the ones that have sustained that segment of their offering and we tend to be much more informed and vigilant about what's going on, and they're going to have to work really hard to win us back,” said our New England Jetta TDI owner.

Volkswagen as a whole will survive, but in the U.S., it betrayed some of its most important customers and they may never win them back.