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Guide to EGR Deletes and Exhaust Modifications

April 11, 2024

The world of emissions and emissions testing is complex and marked by regulations and controversy. A deeper look into the topic is essential for those considering bypassing emission testing or performing emission deletes on trucks and equipment.

Significant risks, including fines and federal prosecution, are underscored by state laws that require understanding and compliance. 

Diesel deletes are the removal or modification of exhaust parts and systems like the EGR, DPF, DEF, and more. This blog post will answer your questions on common delete types, their function, why some consider them, and the legal and environmental implications involved.

We can't provide legal advice on this matter, but we encourage you to follow all Environmental Protection Agency and Department of Motor Vehicle guidelines regarding emission equipment standards. 

Deleting a Diesel

An emissions delete involves removing or modifying emissions-reducing parts from a vehicle's exhaust system to improve performance. Though they improve performance, diesel deletes are illegal at a federal level because they modify regulated parts of the exhaust system, increasing harmful pollutants in the air. Below is a list of common types of deletes.

EGR Delete:

EGR refers to the Exhaust Gas Recirculation Valve, designed to recirculate the exhaust gas back to the cylinders to decrease the amount of nitrogen oxide (NOx) released into the atmosphere. Many opt to remove this valve. Deleting EGR systems is illegal in all 50 states, as it reintroduces harmful NOx into the atmosphere. 

DPF Delete:

A DPF, also known as a Diesel Particulate Filter, is designed to capture soot and particulate matter in exhaust gases. Performing this delete can increase fuel efficiency and horsepower, but the soot and particulate matter that would have been trapped is now also released into the atmosphere.

DEF Delete:

This delete bypasses or removes the SCR system, which is intended to use DEF (Diesel Exhaust Fluid) to reduce nitrogen oxide emissions from diesel exhaust. Doing this reduces maintenance but also increases emissions and violates environmental laws in many jurisdictions at the state and federal levels.

Why do some consider deletes?

Now that we've discovered the common types of deletes and what each does, let's look at the reasons leading up to many individuals performing deletes on their equipment, legal considerations aside. 

Engine Performance

Some individuals view emissions deletes as a cost-saving measure for future repairs. According to Tuner Depot, DPFs can accumulate dirt and obstructions over time, potentially causing engine issues. Performing a DPF delete could prevent such complications and result in savings and less downtime. 

In research findings, a benefit often associated with EGR deletes is enhanced airflow to the engine, potentially resulting in improved performance.

Maintenance and Engine Life

According to Diesel Doctor, completing the deletion can enhance fuel efficiency by updating power levels to the original state, increasing engine power, and lengthening the engine’s life.


Overall, most consider deletes in hopes of improving fuel efficiency, performance, and overall engine longevity. Next, let's review the enforcement alert the Environmental Protection Agency issued.

Environmental Protection Agency (EPA) Enforcement Alert

Many people wrongly believe that common emission modifications are legal, but altering or removing exhaust equipment is actually quite illegal at the state and federal levels. The EPA monitors violations closely for individuals and businesses and publishes them yearly on its website

In December 2020, the EPA introduced a new enforcement alert to notify and remind regulated businesses that tampering with or removing parts mentioned in the above section or adding defeat devices could be expensive and include penalties. The EPA is concerned that the bans listed in section 203(a)(3) of the Clean Air Act and 40 C.F.R. §§ 1068.101(b) are continually ignored.

The Clean Air Act stipulates that any manufacturer of engines or vehicles must not circumvent the emission limits set in place. It also prohibits the creation, sale, or installation of components that bypass or defeat emission controls. The EPA believes that adding these defeat devices or proceeding with deletion processes creates poor air quality, ultimately affecting public health.

Several tests the EPA has run show that devices installed with defeat devices create more air pollution than those in compliance with regulations. The EPA acknowledges within its enforcement alert that some individuals or companies can have what it refers to as a “reasonable basis.” This term refers to the EPA taking no action against companies or individuals who can prove that any parts they create or sell have no adverse effect on emissions. "Reasonable basis" requirements include...

  • The part must have the same design and working order as it was replaced.
  • Emission standards are met precisely as when performed by the OEM and used to verify with the EPA certifications.
  • CARB - California Air Resources Board has created an executive order considering the same part on the exact model vehicle on which somebody added the original part.


Now that we've discovered the EPA Enforcement Act, let's move on to the legal consequences of tampering with or removing emissions equipment.

Warranty & Legal Consequences

It's important to know that moving forward with deletions on equipment or vehicles will void the powertrain warranty. The powertrain warranty typically pays off certain repairs or replacement parts at the beginning of a machine's life, including the engine and transmission, so voiding this could prove costly. 

Changes to any portion of the emission programs on equipment and vehicles have legal ramifications. The EPA monitors violations and violation reports closely and ensures that businesses or individuals practicing deletes are subject to penalties. Deleting the systems is illegal, violates state and federal regulations, and results in fines that the party must pay.

According to an article by Clean Air Northeast, a range of violations occur, and penalties for those can be weighty. Anyone selling or installing parts that go around emission controls could be fined $5000 or more per device. If a dealer tampers with defeat devices, they can be subject to $5000 or more per vehicle.

Not only are there federal regulations, but state and local levels exist as well. The northeastern states typically require vehicle inspections to ensure all systems are intact—other states complete emissions inspection programs. The regulations are stricter in areas that must comply with federal air quality standards. If someone is unsure whether or not their asset has been tampered with, some places like the Minnesota Pollution Control Agency provide details as to what to look for; if something is located, the customer can apply lemon laws to aid in reporting. 

In Review

We hold making informed decisions close to our hearts, especially when removing emission requirements from equipment or vehicles. We understand that not only is this practice illegal, but it's also heavily regulated and monitored by the EPA, affecting both individuals and businesses alike. It's a sensitive area, and while we can't offer legal advice, we want to stress the importance of adhering to all EPA and DMV guidelines regarding emissions equipment standards.

Diesel pickups, construction and agriculture equipment, and freight vehicles are each deleted at varying rates, with semi-trucks being the most frequently modified. The legality of these modifications hinges on the vehicle's operational context (on-road vs. off-road), its type, and adherence to local and federal environmental regulations, underscoring the importance of compliance in vehicle and equipment modifications.

As an auction company, we operate on a principle of transparency, selling items "as is, where is." We ensure that all our knowledge about the equipment and vehicles is clearly posted on each item listing. But it's not just about us; it's about staying informed. Regulations are constantly evolving, becoming stricter with each passing year. It's crucial to remain vigilant and keep knowledgeable of all regulations at both the federal and state levels. If bidding online at Purple Wave, be sure to consult the listing and buyer to be assured it hasn't been previously deleted. 


How to avoid DPF problems?

To help prevent DPF issues, regularly maintain and use the correct fuel, avoid short trips, and monitor any warning lights. While some opt for an illegal DPF delete to prevent maintenance, proper care can lead to longevity while complying with emissions regulations.

What is a deleted truck?

A "deleted" truck refers to a vehicle that has specific emission control components like the DPF (Diesel Particulate Filter), EGR (Exhaust Gas Recirculation), or SCR (Selective Catalytic Reduction) systems removed or disabled. This is widely illegal, due to deletes contributing to increased emissions, but it is often done to increase performance and fuel efficiency.