The revelation that Volkswagen manipulated its software to get its diesel cars to pass emissions standards could cost the company dearly - it faces the prospect of lost sales, a massive fine and a sullied reputation.
But the impact on owners of the nearly 500,000 vehicles involved is less certain, as regulators continue to investigate and the company hasn't yet said how it will bring cars into compliance.
That's raised considerable alarm among diesel owners, many of whom were drawn to the cars because they feature high gas mileage and have been marketed as "clean" technology.
Here are answers to some questions you might have.
What cars are involved in the investigation?
First off, if your car doesn't have a diesel engine, you're squared away. That includes most VW owners; about three-quarters of the cars the automaker sells are standard gasoline vehicles.
If you bought a diesel VW in the last few years, though, your car might be affected. That includes about 482,000 cars, starting with the model year 2009.
Here's the list of cars investigators are looking at: VW Beetle, Golf and Jetta and the Audi A3, from model years 2009 to 2015. They're also looking at the VW Passat in model years 2014 and 2015.
What can I do now?
Unfortunately, not a whole lot.
More than likely, VW will end up recalling these cars, meaning you'll probably have to take your car into the shop to bring it into compliance. So far, though, the company hasn't announced how it will go about doing that.
In a statement after the news broke last week, VW said: "We are working to develop a remedy that meets emissions standards and satisfies our loyal and valued customers. Owners of these vehicles do not need to take any action at this time."
Meantime, VW and regulators have emphasised that these cars are still legal and safe to drive.
How bad is the problem?
Aside from the sheer number of cars affected, the level of emissions violations raised by regulators is fairly dramatic.
The United State Environmental Protection Agency says these cars were emitting nitrogen oxides, or NOx, at 10 to 40 times the level allowed by US federal law.
Nitrogen oxides, by the way, contribute to ground-level ozone pollution and can aggravate respiratory diseases such as asthma.
What should I keep an eye on as the situation progresses?
The big question looming over VW's diesel cars now is how the company will lower emissions and whether their performance will suffer as a result.
Diesel engines have grown a fan base around the gas mileage they offer and the power they produce, so if VW has to tone down either, that could anger the company's fans. And that could end up affecting the cars' resale value.
Already, commenters on the VW diesel-focused forum TDIclub.com have begun wondering whether they can get away with ignoring a recall that would fix the problem. And in a sign of what's to come, a handful of law firms have filed class-action lawsuits against VW.