The organization, known by its German initials, E.U.G.T., did not do any research itself. Rather, it hired scientists to conduct studies that might defend the use of diesel. It sponsored research that challenged a 2012 decision by the World Health Organization to classify diesel exhaust as a carcinogen. It financed studies that cast doubt on whether banning older diesel vehicles from cities reduced pollution. It produced a skeptical assessment of data showing that diesel pollution far exceeded permitted levels in cities like Barcelona, Spain.
Industries like food, chemicals and pharmaceuticals have a long history of supporting research that advances their political agendas. But the automakers’ group consistently promoted the industry’s claim that diesel was environmentally friendly — a claim now undercut by the Volkswagen scandal.
Margaret Douglas, the chairwoman of a panel that advises the Scottish public health system on pollution issues, compared the automakers’ behavior to the tobacco industry. Just as the tobacco companies promoted nicotine addiction, Ms. Douglas said, the carmakers lobbied for tax breaks that made European drivers dependent on diesel.
“There are a lot of parallels between the industries in the way they try to downplay the harm and encourage people to become addicted,” Ms. Douglas said.
Volkswagen, Daimler and BMW said the research group did legitimate scientific work. “All of the research work commissioned with the E.U.G.T. was accompanied and reviewed by a research advisory committee consisting of scientists from renowned universities and research institutes,” Daimler said in a statement.
Daimler and BMW said they were unaware that the Volkswagen used in the Albuquerque monkey tests had been set up to produce false data. Volkswagen said in a statement that the researchers had never managed to publish a complete study.
It wasn’t for lack of trying.
Documents produced in legal proceedings show that in August 2016 Michael Spallek, the director of the automakers’ research group, emailed the Lovelace Respiratory Research Institute, the Albuquerque organization that conducted the tests with monkeys. “The E.U.G.T. point of view is that it’s time to try to finalize the report and to present or discuss the problems of the study in a scientific way ASAP,” Mr. Spallek wrote.
That was almost a year after Volkswagen admitted to equipping millions of diesel vehicles sold in the United States and Europe with illegal “defeat devices” that cranked up pollution controls when software detected that testing was being done in a lab. At other times, the controls were turned off, allowing the cars to produce more nitrogen oxides than a long-haul truck.
Mr. Spallek declined to comment, saying his contract prohibited him from discussing the research group’s work.
In the 1990s, carmakers used their political clout to persuade European leaders that diesel helped fight climate change because it burns more efficiently than gasoline. As a result, almost all European countries now tax diesel at a lower rate than gasoline, making it cheaper at the pump.
The carmakers maintained that modern technology had solved diesel’s big downside: emissions of nitrogen oxides and fine soot particles that can contribute to asthma, heart attacks and cancer.
David King, a former chief scientific adviser to the British government, recalled being taken to a lab in the early 2000s where 10 diesel vehicles were running on rollers. The air was so clean that Mr. King, an asthmatic, could breathe freely.
What Mr. King did not know is that most European automakers had built their diesel cars to pass laboratory emissions tests and no more. On the road, according to recent studies by the governments of Britain, France and Germany, diesel cars by almost all European manufacturers spewed toxic gases in quantities far above those allowed by law.
“We were all misled by the car manufacturers,” Mr. King said in an interview.
The toll on public health has become impossible to ignore. In 2012, 72,000 people in Europe died prematurely because of nitrogen dioxide pollution, which comes primarily from diesel vehicles, according to a report released last year by a committee of the European Parliament.
Research sponsored by industry “all has the same fundamental aim,” said Joachim Heinrich, an environmental health expert at the University of Munich who has spent his career studying the effects of air pollution, “namely to weaken or discredit regulation — to say ‘the evidence is not that clear,’ ‘we shouldn’t take it so seriously,’ ‘we need to think more about it.’”
The automakers’ research group was created in 2007, as Volkswagen was readying a major push to market diesel technology in the United States, which has stricter limits on nitrogen oxide emissions than Europe. Mr. Spallek, the executive director, had been the chief medical officer of Volkswagen’s commercial vehicles division.
The negative health effects of diesel were starting to attract more attention. Zones where diesel was restricted were proliferating in Europe, posing a threat to automakers because the areas discourage sales of diesels.
In response, the research group financed two studies that concluded that low-emissions zones had only a marginal effect on pollution levels. But the studies used dubious methodology, the German Federal Environment Agency said in a report released last year.
The industry group’s studies on low emissions zones were influential, however. They were cited in reports by the Organization for Economic Cooperation and Development, and by the National Institute for Health and Care Excellence, a public body in Britain that provides guidance on health care.
Elsewhere, a regional court in Austria cited the research in a 2014 ruling against residents of Graz who had sued to force officials to restrict diesel traffic. The decision, by the State Administrative Court for the province of Styria, called the study “thorough” and said it showed that the effect of low-emissions zones on fine soot pollution was “less than expected.” The decision did not mention that the study had been financed by the auto industry.
Officials at the research group also sought to influence public debate. In 2016, Helmut Greim, the chairman of the group’s research advisory board, testified before the German Parliament that it was impossible to establish a direct link between nitrogen dioxide pollution and lung ailments. Mr. Greim is a longtime bête noire for environmental activists, who say he consistently takes the industry point of view.
Mr. Greim, 82, said in an interview that the group’s research was independent and published only in peer-reviewed journals. During an interview in Munich, he said that fear of nitrogen dioxide pollution was “completely overblown.”
The research group intended the Albuquerque experiment to be a rebuttal to a 2012 finding by a division of the World Health Organization that had classified diesel exhaust as a carcinogen.
The automakers’ research group set out to show that new diesel vehicles were better. It hired the Lovelace Respiratory Research Institute, an established research center that has also done work for the Environmental Protection Agency, to conduct a study that would compare emissions from a late-model Volkswagen with those of a 1999 Ford diesel pickup.
The tests were conducted in 2014 using 10 cynomolgus macaque monkeys, a breed used extensively in medical experiments, according to the legal records.
Volkswagen took a lead role in the study. Company engineers supervised the installation of a treadmill that would allow the vehicles to run on rollers while equipment sucked exhaust from the tailpipes.
The gas was then diluted and fed into chambers containing the monkeys. To keep the animals calm during the four hours they breathed fumes, lab workers set up a television showing cartoons.
“They like to watch cartoons,” Jake McDonald, the Lovelace scientist who oversaw the experiments, said in a sworn deposition taken last year as part of a lawsuit by Volkswagen diesel owners seeking damages beyond those provided for in a class-action settlement.
Dr. McDonald said he did not know the Volkswagen Beetle was equipped with software that recognized when the car was being tested on a treadmill. The software did not interfere with the filter that removed carcinogenic fine soot particles from the exhaust, a technology that has in fact improved significantly.
But it cranked up controls so that nitrogen dioxide pollution, which has been linked to asthma, bronchitis, heart attacks and possibly lung cancer, was only a small fraction of what it would be during normal driving.
Even so, the study did not provide a clear finding. The researchers struggled to produce a paper that they could publish, a condition for receiving full payment.
In the August 2016 email, Mr. Spallek complained about numerous flaws with the methodology used by the Lovelace research team. But he never mentioned the illegal software that had caused the Beetle to produce artificially low emissions.
Discussions about publishing the study continued until last year, according to Dr. McDonald. A lawyer for Volkswagen, Michael Steinberg, implied during cross-examination that Dr. McDonald had pushed to publish the results so that the institute could collect $71,000 owed under the contract.
Dr. McDonald disputed that assertion. “The decision to continue,” he said in an emailed statement, “was the choice of the client.”
Although Dr. McDonald and other employees at the institute exchanged emails about the Volkswagen defeat device after its exposure in 2015, Dr. McDonald testified that he had not followed the Volkswagen case closely and had realized only recently that the Beetle used in the tests was manipulated to produce artificially low emissions.
“I feel like a chump,” Dr. McDonald said.