LONDON — A loyal Volkswagen owner for years, Jane Kelley was “shocked,” she says, by recent revelations that the German company had cheated on emissions tests in the United States.

Snug in Ms. Kelley’s garage in North London recently was a white 2013 Passat powered by a 2-liter diesel engine. The company says that as many as 11 million of its cars — Volkswagens, Audis, Skodas and SEATs with diesel engines — were equipped with software designed to fool emissions testers.

But as disturbed as she was to learn that Volkswagen had cheated, Ms. Kelley does not necessarily want anything done about it. “Are they going to take my car away and fiddle with the engine?” she said with a worried tone, as she served tea in her sunlit dining room.

As with at least some European diesel drivers, Ms. Kelley is in no hurry to abandon the car just because it may spew more noxious fumes than she originally thought. “I do feel that it is a very safe car,” she said. She also admires the acceleration of the turbocharged diesel, which she credits with helping her recently escape a potential hazard. “There was a guy weaving, maybe drunk, so I just shot by,” she recalled.

Ms. Kelley is one of millions of fans of diesel cars across Europe, where fuel prices and taxes make the cost of filling an automobile’s tank much higher than in the United States. Drawn by diesels’ superior fuel economy over gasoline engines and the lower price of diesel fuel, European consumers have long leaned toward diesel cars — a collective habit that might be difficult to break, despite the new scrutiny the Volkswagen scandal has given to diesel’s dark side.

While diesels have struggled in the United States to overcome a reputation as smoke-belching clunkers — they represent about 3 percent of the American car market — they have rolled to dominance across the Atlantic. Diesels accounted for more than half the new cars sold in Western Europe last year, compared with 14 percent in 1990.

Europeans’ embrace of diesels has encouraged manufacturers to improve the engines’ performance, and it has motivated governments, especially those of Germany and France, to support their auto industries’ diesel efforts. Although environmentalists have been sounding alarms for years, the forces propelling diesel were so strong that it might explain why drivers, carmakers and regulators have been willing at times to overlook diesels’ tendency to be bigger polluters than gasoline cars.

“Ban diesels? You can’t be serious,” Ségolène Royal, the French environment and energy minister, said recently, responding to a suggestion by a member of the Green Party. “We can’t treat problems of this gravity with ideological slogans at the expense of French interests,” Ms. Royal said, noting that more than half the cars on French roads were diesels.

In fact, the percentage in France is around 64 percent, even higher than in Germany, with French-made Renault, Peugeot and Citro渀 diesels joining Volkswagens on the road. There has been no indication that the French automakers cheated on emissions tests.

So far, Volkswagen has not said how it plans to deal with the deceptive software problem, although the German government has set an Oct. 7 deadline for the company to propose a solution. Unlike in the United States, where lawyers are already recruiting car owners in hopes of filing class-action lawsuits, there is no similar tradition in Europe that would encourage consumers to collectively demand financial redress.

Volkswagen said on Tuesday that it would prepare a plan by early October to improve the emissions of affected vehicles. Owners will be notified in the weeks and months after the plan has been approved by authorities, the company said.

“If there is a recall, I would be happy if my car is not included in it,” said Tony Novak, a retired editor for the BBC who lives in Reading, England. In Britain, just over half of new cars sold are diesels.

“Diesels used to be terrible — they used to be dirty and slow,” he said. “Now they are brilliant.” Mr. Novak had owned diesel cars previously, but when he bought his 2014 Volkswagen Golf diesel, “I was really surprised by how good it was — you really notice the difference in acceleration.”

That Volkswagen might have achieved that performance by cheating — it is still not clear whether the company needed the deceptive software to pass Europe’s emissions tests, which are much less strict than the United States’ — is not what matters most to Mr. Novak. “I worry that if they tweak the computer, the performance will deteriorate,” he said.

About five million of the affected cars are Golfs, Passats and other Volkswagen-brand cars. An additional two million are Audi brand cars, and the rest or Skoda and SEAT brand cars, or light commercial vehicles.

Matthias Müller, a company insider who was appointed chief executive of Volkswagen last week, told top managers late Monday that the deceptive software was activated in only a portion of the 11 million vehicles that have the so-called EA 189 diesel motors. But Volkswagen did not specify how many cars were designed to cheat on emissions tests.

Some industry experts say that the Volkswagen scandal could prove a turning point in the diesel love affair, if the new scrutiny of European emissions standards and testing makes it easier for the environmentalists to be heard.

The premise of the “clean diesel” notion that Volkswagen promoted was partly based on the fact that on a per-mile basis, diesel engines emit less carbon dioxide — a big contributor to climate change — than gasoline engines. But diesel exhausts, unless cleaned in ways that Volkswagen’s software was designed to sidestep, produce larger quantities of other harmful gases — nitrogen oxides — along with fine particles that contribute to stubbornly persistent air quality problems in European cities.

“There is a recognition that, fundamentally, it is going to be difficult to control all of the problems with diesel — smoke production is not going to go away,” said Peter Wells, co-director of the center for automotive industry research at Cardiff Business School. “In the very long term, diesel has had its day.”

According to the European Environment Agency, which monitors air quality, 20 to 30 percent of urban residents in Europe are exposed to particle levels — mainly from diesel exhaust fumes — above those considered safe by the European Union, while about 10 percent are exposed to unsafe levels of nitrogen oxides.

London and Paris have among the highest pollution levels in terms of nitrogen oxides. In March of this year and last, the smog in Paris reached such levels that the authorities were forced to temporarily limit the number of cars on the road each day.

Anne Hidalgo, the mayor of Paris, which is playing host to the United Nations climate conference in November, is among those who have suggested an eventual ban on diesels in the city.

The mayor of London, Boris Johnson, plans to establish an ultralow emissions zone in London by 2020 where older diesels will be penalized. A recent report by the environmental committee of the London Assembly, the city’s legislature, said the mayor should consider banning all diesels from the zone.

But environmental efforts must contend with deeply rooted diesel economics. Automotive fuel in Europe costs several times as much as in the United States, mainly because of higher taxes. The average price of gasoline in London in August, for example, was 521 pence, or about $7.92, per gallon. In most of Continental Europe, diesel sells for about 15 percent less than gasoline.

Part of that difference is because the taxes that help keep fuel prices high are typically lower on diesel fuel.

In Germany, the lower taxes on diesel fuel amount to an annual subsidy of 7 billion euros, or about $7.8 billion, for diesel owners, said Daniel Moser, a transportation analyst for the environmental group Greenpeace.

“These policies are not in accordance with what we would have to do to protect the environment and people’s health,” he said.

And then there are vehicle tax breaks that various governments offer to diesel owners, because of the cars’ lower emissions of carbon dioxide.

Also, new diesels are often only slightly more expensive than their gasoline counterparts. In Britain, a Volkswagen Golf Match with a 1.4-liter, turbocharged gasoline engine sells for 20,955, or about $31,800, while a similar model with a 1.6-liter diesel engine sells for 21,960, according to Carbuyer, a British website.

With all those factors taken into account, owning and operating a diesel car in Europe is the more affordable way to go.

In the United States, with much lower gasoline prices, “there is no point at the margin, buying a diesel,” said Garel Rhys, a professor emeritus at Cardiff University. He said Europeans’ embrace of diesels made perfect sense. “Essentially, growth came because consumers are economically rational individuals,” Professor Rhys said.

But a continued yen for diesels may not necessarily translate into an abiding love of Volkswagen, for some Europeans at least.

Jon Devereux, who drives a diesel-engine Volkswagen Touareg, manages a hotel in Milford on Sea, in southern England. Each winter, he takes the four-wheel-drive vehicle to his winter home in the French Alps. The Touareg, he said, has “been brilliant for 10 years.”

But when it comes time to replace it, his next diesel will not be a Volkswagen. The emissions scandal has soured Mr. Devereux on the carmaker. “Would you buy a VW car or any car in the VW group?’’ he asked.