– At the Volkswagen of Oakland dealership, the German company's "clean diesel"-powered cars were a big hit with eco-friendly customers.

Now, after VW's admission that it rigged emissions tests of its diesel cars in the United States, a line of 2015 diesel Golf Sportwagens sit unsellable in the lot, because sales are suspended until further notice.

"We definitely feel betrayed," said sales manager Chris Murphy, calling the scandal "a hit for the brand."

The world's biggest carmaker by sales told the Environmental Protection Agency that it used special software to lower emissions during vehicle inspections by U.S. regulators.

"I'd be [angry] if I were a consumer. A lot of people may have bought it for the eco-friendly elements," Murphy said.

Although consumers in all states are affected, the sting is particularly acute in California, which prides itself on its environmental record and where most VW diesel car owners live.

Californians own 14 percent of all VW diesel cars affected in the scandal, compared with Texans at 7 percent and Floridians at 5.7 percent, according to Kelley Blue Book.

California's regulators were first alerted to emissions problems in VW's diesels in 2014.

With VW's disclosure on Tuesday that 11 million cars are affected, both auto dealers and owners are reeling, with irate consumers flooding Twitter with a #BoycottVW hashtag and online forums for diesel fans abuzz with anger and skepticism.

"Thanks to VW's blatant and intentional fraud, I am now the subject of ridicule for having bragged about my good gas mileage and reliability," wrote one owner on the VW Vortex forum.

VW diesel enthusiast Fred Voglmaier, whose TDI Club forum saw over 2,000 posts on the topic since Friday, said owners worry about loss of performance if VW performs a fix, as well as resale value.

"There is a lot of angst and wild guessing as no one really knows what is going to happen," Voglmaier said. "It's created a bit of a panic among some, no matter what the outcome is. Many feel cheated by Volkswagen."

For now, car owners and dealers aren't sure whether VW will allow trade-ins of the cars or have them fixed.

A letter sent by VW on Monday to its U.S. dealers and seen by Reuters says a "mandatory stop-sale order" is in effect for 2009-2015 models with a two-liter diesel engine.

"Volkswagen is currently working on a remedy to address this issue," the letter said. It said dealers will be reimbursed for expenses.

Dealers can advise owners "the matter under investigation … does not involve a defect relating to safety," VW said, adding owners "do not need to take action at this time."

The EPA on its website said VW will likely send owners a recall notice but that cars were "safe and legal to drive."

For now, dealer Murphy said he doesn't know what to tell his customers, who may demand a refund or exchange for their car.

"We can't take the hit for it," he said. "That would put us out of business."

Owner Voglmaier said the bigger question is what the fallout means for diesel cars in North America.

"It's been a long road and finally it has started to gain better traction and acceptance," he said. "Now this could be a huge setback … for all manufacturers and not just Volks­wagen."