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What is the diesel emissions scandal? Understanding the controversy and its impact

Close-up of a car exhaust pipe pumping out a white cloud of diesel emission fumes.

What is the diesel emissions scandal? The diesel emissions scandal, also known as “Dieselgate,” refers to a widespread controversy that shook the automotive industry, involving the manipulation of emissions testing results by major automakers.

This scandal, which first came to light in 2015, exposed the use of emissions-cheating devices by several prominent car manufacturers. The revelation shocked consumers, regulators, and the general public, leading to significant legal and financial consequences for the implicated companies.

In this blog post, we’ll delve into the intricacies of the diesel emissions scandal, examining its origins, impacts, and the lessons learned from this pivotal event.

Significance and impact of the diesel emissions scandal on the automotive industry

The diesel emissions scandal had far-reaching consequences that significantly impacted the automotive industry. So, what is the diesel emissions scandal, and how did it impact the industry? Let’s delve deeper into the significance and ramifications:

Loss of consumer trust

The diesel emissions scandal shattered the trust of consumers who believed that diesel vehicles were cleaner and more environmentally friendly. The revelation that emissions were manipulated eroded confidence in automakers and their claims.

Reputation damage

The scandal tarnished the reputations of the automakers involved, leading to significant financial losses and plummeting stock values. Companies faced substantial fines, legal settlements, and costly recalls, which strained their resources and impacted future investments.

Stricter regulations

The diesel emissions scandal prompted regulators worldwide to re-evaluate emission standards and testing procedures. Governments implemented stricter regulations to ensure accurate testing and reduce emissions, leading to increased scrutiny and compliance requirements for automakers.

Environmental impact

Diesel emissions contribute to air pollution and have detrimental effects on both the environment and public health. The scandal highlighted the need for better control and reduction of harmful pollutants to mitigate these negative impacts.

Shift towards electric and alternative fuels

Because of the diesel emissions scandal, there has been a heightened focus on alternative fuel sources, such as electric and hybrid vehicles. Governments and consumers have increasingly supported cleaner and more sustainable transportation options.

The diesel emissions scandal serves as a stark reminder of the importance of transparency, regulatory oversight, and ethical practices within the automotive industry. It’s prompted significant changes in the way automakers operate and has accelerated the transition towards greener, more sustainable transportation solutions.

What is the diesel emissions scandal and how did it unfold?

The diesel emissions scandal began in the quest for automakers to meet stringent emission standards while maintaining performance and fuel efficiency. In the early 2000s, diesel engines gained popularity due to their lower carbon dioxide (CO2) emissions compared to gasoline engines. However, they produce higher levels of nitrogen oxides (NOx) and particulate matter (PM), which are harmful pollutants.

The diesel emissions scandal began to unravel in September 2015 when the United States Environmental Protection Agency (EPA) issued a notice of violation to Volkswagen (VW) for using software to cheat emissions tests. VW had installed a defeat device in their diesel vehicles, which detected when the vehicle was undergoing testing and adjusted its performance to meet emission standards. However, during real-world driving conditions, the vehicles emitted significantly higher levels of pollutants.

As the investigation into VW progressed, it became evident that other automakers were also involved in similar practices. Renault, among others, faced scrutiny regarding its diesel emissions. The scandal exposed a widespread problem of cheating on emissions tests and raised questions about the integrity of regulatory compliance in the automotive industry.

Discover more about the history of the diesel emissions scandal.

Who was involved in the diesel emissions scandal?

The diesel emissions scandal involved various key players, so who exactly was involved in the diesel emissions scandal? Let’s take a closer look:


Volkswagen was at the centre of the scandal, with millions of their vehicles equipped with defeat devices. Other automakers, such as Renault, also faced allegations of using similar tactics to manipulate emissions test results.

Regulatory bodies

Regulatory bodies played a crucial role in uncovering the scandal and holding automakers accountable. The United States Environmental Protection Agency (EPA), and the California Air Resources Board (CARB) conducted investigations that led to the exposure of VW’s emissions cheating. In addition to these US bodies, regulatory bodies in the UK and EU also played a significant role in uncovering the scandal and taking regulatory action.

Consumer organisations and activists

Consumer organisations, such as consumer protection agencies and environmental non-governmental organisations (NGOs), played a significant role in raising awareness about the scandal. They advocated for stricter regulations, transparency, and accountability from automakers.

Which were the main car manufacturers affected by the diesel emissions scandal?

The diesel emissions scandal had a significant impact on several major automakers. So, what is the diesel emissions scandal, and which car manufacturers were affected? Let’s find out:

Volkswagen (VW)

VW was at the epicentre of the scandal, with millions of their diesel vehicles equipped with defeat devices. The company faced substantial financial losses, incurred hefty legal penalties, and had to initiate massive recalls.


Renault, a prominent French automaker, faced allegations of manipulating emissions test results in some of its diesel vehicles. The scandal tarnished the company’s reputation and raised questions about its practices.

Other automakers

The diesel emissions scandal prompted broader investigations into emissions compliance across the industry. Other automakers, such as Fiat Chrysler, Mercedes-Benz, and BMW, also faced allegations and scrutiny related to their diesel emissions.

The revelations sparked a significant shift in the industry’s approach toward emissions control, compliance, and transparency.

What is an emissions-cheating device?

Emissions cheating devices, also known as defeat devices, are mechanisms or software installed in vehicles to manipulate emission test results. Their purpose is to deceive regulatory authorities and make the vehicles appear compliant with emission standards during laboratory testing, while in real-world driving conditions, they emit higher levels of pollutants.

These devices operate by detecting when the vehicle is undergoing emissions testing. They can alter engine performance, emissions control systems, or exhaust gas treatment to achieve lower emission levels during testing. Once the test is complete, the device reverts to normal operation, emitting pollutants at higher levels.

The primary goal of these cheating devices is to ensure that vehicles meet the regulatory emission standards without sacrificing performance or fuel efficiency, thereby avoiding costly modifications or compromises in vehicle design.

How were the defeat devices discovered?

The discovery and exposure of emissions-cheating devices were the results of a combination of factors, including independent research, regulatory investigations, and whistleblowers.

Independent research

Independent organisations and researchers, such as the International Council on Clean Transportation (ICCT) and West Virginia University, conducted real-world emissions tests to verify discrepancies between laboratory results and on-road emissions. These tests revealed unusually high emission levels in certain vehicles, leading to suspicions of manipulation.

Regulatory investigations

Regulatory bodies, including the EPA, CARB, UK’s DVSA, and EU bodies, launched investigations into vehicle emissions compliance following the initial revelations regarding VW. They conducted extensive testing and analysis to detect discrepancies between laboratory results and real-world emissions.

Whistleblowers and insider information

Whistleblowers from within the automotive industry played a significant role in exposing the presence of emissions-cheating devices. Insiders who were aware of the manipulation practices came forward with crucial information, providing evidence to support the allegations.

How did the automakers manipulate emissions test results?

Automakers employed various cheating methods to manipulate emissions test results. While specific methods varied, they generally revolved around exploiting the testing conditions or tampering with emission control systems. Some examples include:

Defeat device software

The most well-known method involved installing software in engine control units (ECUs) to detect when the vehicle was undergoing emissions testing. The software would activate specific parameters, reducing emissions during the test but allowing higher levels of pollutants during normal driving.

Temperature and speed manipulation

Some vehicles were programmed to detect specific test conditions, such as ambient temperature and vehicle speed, to adjust engine operation and emissions control systems. This manipulation aimed to optimise emissions performance during testing while allowing higher emissions during regular driving.

Extended emission strategies

Certain vehicles utilised extended emission strategies that allowed emissions control systems to temporarily operate optimally during the initial phases of testing but deactivated or performed sub-optimally during prolonged real-world driving.

These are just a few examples of the methods used to cheat emissions tests. The complexity and variety of cheating techniques highlight the deliberate efforts made by automakers to circumvent regulations and mislead regulators and consumers regarding the true emissions performance of their vehicles.

The environmental impact of increased diesel emissions

The diesel emissions scandal has had significant environmental implications, primarily due to the increased emission of pollutants, such as nitrogen oxides (NOx) and particulate matter (PM), from affected vehicles. These pollutants contribute to air pollution and have adverse effects on the environment, including:

Air quality degradation

Diesel emissions significantly contribute to poor air quality, especially in urban areas. The release of NOx and PM can lead to the formation of smog and particulate pollution, which have detrimental effects on human health and ecosystems.

Contribution to climate change

Diesel engines emit greenhouse gases, including carbon dioxide (CO2) and other climate-forcing pollutants. The increased emissions resulting from the scandal have contributed to global warming and climate change, exacerbating the environmental crisis.

Damage to ecosystems

Pollutants from diesel emissions can harm plants, animals, and ecosystems. Acidification of soil and water bodies, as well as the deposition of PM on vegetation, can impact biodiversity and disrupt ecological balance.

Health risks associated with diesel emissions

Diesel emissions pose significant health risks, particularly due to the presence of NOx, PM, and other harmful pollutants. The health implications include:

Respiratory problems

Exposure to diesel emissions can cause or worsen respiratory conditions such as asthma, bronchitis, and chronic obstructive pulmonary disease (COPD). The fine particles in diesel exhaust can penetrate deep into the lungs, leading to inflammation and respiratory irritation.

Cardiovascular effects

Diesel emissions have been linked to cardiovascular diseases, including heart attacks, strokes, and increased blood pressure. Inhalation of PM and other pollutants can trigger inflammation, oxidative stress, and damage to the cardiovascular system.

Increased cancer risk

Diesel exhaust contains carcinogenic substances, such as benzene and formaldehyde. Prolonged exposure to these compounds increases the risk of developing lung cancer and other forms of cancer, including bladder and kidney cancer.

Find out more about the impact of diesel emissions on health and the environment.

What action has been taken by governments and regulatory bodies in response to the diesel emissions scandal?

The diesel emissions scandal prompted governments and regulatory bodies worldwide to take action by addressing the issue and preventing similar scandals from occurring in the future. Key actions include:

Strengthened emissions testing and regulations

Governments and regulatory bodies implemented stricter testing procedures to ensure more accurate measurement of emissions during real-world driving conditions. This included the introduction of on-road emissions testing and the use of portable emission measurement systems (PEMS) to supplement laboratory tests.

Increased transparency and accountability

Regulatory bodies emphasised the importance of transparency and accountability in the automotive industry. They pushed for clearer reporting of emissions data, stricter auditing processes, and enhanced oversight to prevent cheating practices.

Emission standards updates

Governments and regulatory bodies revised and tightened emission standards for vehicles, both in terms of NOx and PM limits. These updates aimed to align the standards more closely with real-world driving conditions and reduce the allowable emissions levels.

What legal action and penalties have the automakers faced?

Automakers implicated in the diesel emissions scandal faced significant legal consequences and financial penalties. Some of the key repercussions include:

Group claims and settlements

Various group-action claims were filed against automakers by affected customers, shareholders, and regulatory bodies. These group claims sought compensation for damages and alleged false advertising. Automakers have reached settlements with claimants, resulting in substantial financial payouts.

Fines and penalties

Regulatory bodies, such as the EPA, CARB, and EU authorities, imposed substantial fines and penalties on non-compliant automakers. These penalties aimed to hold the companies accountable for their wrongdoing and deter similar misconduct in the future.

Recalls and remediation

Automakers were required to initiate massive recalls of affected vehicles to rectify the emission cheating issues. These recalls involved software updates, modifications to emission control systems, and, in some cases, hardware replacements. The cost of recalls and remediation further added to the financial impact on the automakers involved.

How are future scandals to be prevented?

Emissions standards and regulations play a vital role in preventing future scandals and ensuring compliance within the automotive industry. Key aspects include:

Stricter emissions testing

The introduction of more rigorous and comprehensive emissions testing procedures helps identify any discrepancies between laboratory results and real-world driving emissions. This enables regulators to detect and address potential cheating practices promptly.

Enhanced enforcement and oversight

Regulatory bodies need to have robust enforcement mechanisms and enhanced oversight to prevent non-compliance. This includes conducting random audits, spot checks, and in-use vehicle testing to ensure ongoing adherence to emissions standards.

International collaboration

Collaboration among regulatory bodies on a global scale is crucial for addressing emissions issues effectively. Sharing information, best practices, and harmonising emission standards can help create a level playing field and discourage automakers from resorting to cheating practices.

Technological advancements

Advancements in emission control technologies, such as improved exhaust after-treatment systems and more efficient engines, can help automakers meet and exceed emission standards. Governments and regulatory bodies can encourage the development and adoption of cleaner technologies through incentives and regulations.

By implementing and enforcing stringent emissions standards and regulations, governments and regulatory bodies aim to prevent future scandals, promote cleaner and more sustainable transportation, and protect public health and the environment. Continuous monitoring, periodic updates to standards, and collaboration with the industry are essential in this ongoing effort.

What is the potential impact on consumer preferences?

The diesel emissions scandal has the potential to influence consumer preferences and purchasing decisions in several ways:

Shift towards cleaner technologies

Consumers may prioritise vehicles with cleaner emissions technologies, such as electric vehicles (EVs) or hybrid models, as a response to the scandal. The focus on sustainability and reduced environmental impact may drive increased demand for greener alternatives.

Enhanced scrutiny and trust

Consumers are likely to become more cautious and discerning when choosing vehicles, placing greater emphasis on environmental performance, and trusting automakers’ claims. There may be an increased demand for transparency and independent verification of emissions compliance.

Strengthened consumer advocacy

The scandal has empowered consumer advocacy groups and organisations to push for stricter regulations, transparency, and accountability within the automotive industry. These groups may continue to play an active role in influencing consumer choices and advocating for sustainable transportation options.

What are the long-term implications of the diesel emissions scandal

The diesel emissions scandal serves as a powerful reminder of the significance of emissions control and the need for accountability within the automotive industry. It has led to important changes in regulations, testing procedures, and consumer awareness. The scandal has increased scrutiny, encouraging both automakers and regulatory bodies to prioritise sustainability, transparency, and emissions compliance.

In the long term, the scandal has reshaped the industry’s trajectory, pushing for greater investment in cleaner technologies, such as electric vehicles and alternative fuels. It has sparked innovation and accelerated the transition towards a more sustainable and environmentally conscious future.

Join the Renault emissions claim

If you’ve been affected by the Renault diesel emissions scandal, it’s important to take action. Consider joining the Renault emissions claim to seek compensation and hold the automaker accountable for its actions. Visit our Renault diesel emissions claims FAQs for more information.

Your voice and participation can contribute to ensuring a cleaner, more transparent automotive industry for the benefit of both consumers and the environment.

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