Volkswagen clean diesel

Volkswagen clean diesel
	FALSE
	"Volkswagen's "clean diesel" cars met strict US and European emissions standards for nitrogen oxides while offering high fuel economy and strong performance."
Domain	Business, Finance & Scams
Tactic	Fraud or Scam; Manipulation;
Era	Current
First seen	2008
Origin	Volkswagen's marketing of its TDI "Clean Diesel" vehicles in the United States from the 2009 model year
Last reviewed	2026-10-26
	Further reading: books on Business, Finance & Scams

The claim that Volkswagen's diesel cars were "clean diesel" was the centerpiece of a marketing campaign that helped the German carmaker sell hundreds of thousands of diesel cars in the United States and millions worldwide. In 2015 US regulators revealed that the cars contained software, known as a defeat device, that detected when they were undergoing emissions tests and switched on full pollution controls only during testing. On the road, the cars emitted nitrogen oxides at up to 40 times the legal limit. The scandal, often called "Dieselgate," cost Volkswagen more than 30 billion euros in fines, settlements and buybacks, led to criminal convictions and accelerated the industry's shift away from diesel cars.

The claim

In the late 2000s Volkswagen set out to expand its share of the US market by promoting diesel cars as an environmentally friendly alternative to hybrids. Its advertising promoted "Clean Diesel" technology, emphasizing low emissions, high fuel economy and performance. The Jetta TDI won the "Green Car of the Year" award in 2009, and the Audi A3 TDI won it in 2010. Volkswagen said its engines met the strict US limits for nitrogen oxides, or NOx, without the urea-based exhaust treatment systems used by some competitors, which added cost and required owners to refill a tank of fluid.

Origin

Engineers at Volkswagen faced a difficult problem: designing a diesel engine that was affordable, fuel-efficient, powerful and compliant with US NOx limits, which were stricter than those in Europe. Instead of solving the problem, they programmed the engine control software to recognize the specific conditions of a laboratory emissions test, such as the pattern of speed, the position of the steering wheel and the duration of the test. When it detected those conditions, the software ran the emissions controls at full strength. In normal driving, it reduced their effectiveness to improve performance and fuel economy.

What the evidence shows

The deception was uncovered almost by accident. In 2013 the International Council on Clean Transportation, a nonprofit research group, commissioned researchers at West Virginia University to test diesel cars on the road using portable emissions equipment, expecting to show that US diesel cars were cleaner than European ones. Instead, the researchers found that two Volkswagen models emitted NOx far above legal limits in real driving, while a BMW model performed much better. Their results were published in 2014 and passed to regulators.

The California Air Resources Board and the US Environmental Protection Agency questioned Volkswagen for more than a year. The company offered technical explanations and a software recall that did not fix the problem. Finally, under pressure, Volkswagen admitted the cars contained software designed to cheat tests. On September 18, 2015, the EPA issued a notice of violation covering about 482,000 cars with 2.0-liter diesel engines. Volkswagen later acknowledged that about 11 million vehicles worldwide had the software. Larger 3.0-liter diesel engines used in Volkswagen, Audi and Porsche models were also found to contain defeat devices.

Volkswagen's chief executive, Martin Winterkorn, resigned within days, while denying personal knowledge of wrongdoing. In January 2017 Volkswagen pleaded guilty in the United States to three criminal felony counts and agreed to pay $4.3 billion in criminal and civil penalties. Separate settlements required it to buy back or fix cars and fund environmental mitigation and zero-emissions infrastructure. Several executives and engineers were charged in the United States and Germany. Oliver Schmidt, a former manager responsible for US environmental compliance, was sentenced to seven years in a US prison. In Germany, criminal cases against former executives continued for years, and Audi's former chief executive Rupert Stadler was convicted in 2023.

Consequences

Nitrogen oxides contribute to smog and fine particle pollution, which are linked to respiratory and cardiovascular disease. Studies estimated that excess emissions from the affected cars would cause dozens of premature deaths in the United States and many more in Europe, where the number of affected vehicles was much larger.

The scandal also led regulators to introduce real-driving emissions testing in Europe and to scrutinize other manufacturers, several of which were found to have engines that emitted far more on the road than in tests. Diesel's share of new car sales in Europe fell sharply, and Volkswagen made a major strategic shift toward electric vehicles, partly funded by the settlement terms.

Why it persists

Dieselgate is a defining example of corporate deception because:

It was engineered. The deception was written into software and deployed across millions of vehicles.
Tests were gamed. The cars were designed to pass the exact procedure regulators used, rather than to meet the standards in practice.
Green branding sold it. Customers who thought they were making an environmentally responsible choice were misled.
Independent testing caught it. Regulators' laboratory testing did not detect the cheat. Real-world testing by independent researchers did.

Lessons for readers

Performance in a test is not the same as performance in the real world. Ask how claims were measured.
Be skeptical of products that seem to deliver every benefit at once without trade-offs.
Green marketing deserves the same scrutiny as any other advertising.
Independent testing matters. Companies that test their own products have incentives to look good.
Corporate cultures that set impossible targets can drive employees to cheat.

Sources

Gregory J. Thompson et al., In-Use Emissions Testing of Light-Duty Diesel Vehicles in the United States, Center for Alternative Fuels, Engines and Emissions, West Virginia University, for the International Council on Clean Transportation (2014).
US Environmental Protection Agency, Notice of Violation to Volkswagen AG, Audi AG and Volkswagen Group of America, September 18, 2015.
US Department of Justice, "Volkswagen AG Agrees to Plead Guilty and Pay $4.3 Billion in Criminal and Civil Penalties," press release, January 11, 2017.
Jack Ewing, Faster, Higher, Farther: The Volkswagen Scandal (W. W. Norton, 2017).
Steven R. H. Barrett et al., "Impact of the Volkswagen emissions control defeat device on US public health," Environmental Research Letters 10, no. 11 (2015).