EPA GHG rollback still makes deleting diesel emissions equipment illegal experts say

EPA’s GHG rollback plan caused truck owners hope to make deleting emissions equipment legal, yet experts say it falls well short of that.

EPA GHG rollback

The EPA GHG rollback announcement on July 29, 2025 was much anticipated with Zeldin promoting the idea going back to March during his so-called big day of deregulation. Zeldin now says they have scientists who dispute the data and findings from the 2009 report.

The 2009 Endangerment Finding identified “six specific greenhouse gases (carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride) endanger public health and welfare by contributing to climate change,” according to the EPA.

It was created while (D) President Obama was in office and commonly attributed from a landmark 2007 U.S. Supreme Court ruling Massachusetts vs the EPA when (R) President Bush was in office.

The 2009 Endangerment Finding enabled several administrations to use the EPA to target GHG emissions as part of the Clean Air Act to further their goals.

What is diesel emissions equipment?

Since the early 2000s, diesel engines have started implementing new emissions equipment to reduce gases emitted which have caused many diesel truck owners a lot of frustration.

Specifically, diesel truck owners point to Exhaust Gas Recirculation (EGR) systems in 2004, Diesel Particulate Filters (DPF) in 2007 and Diesel Exhaust Fluid (DEF) in 2010 are identified as key problem areas for diesel engines.

These systems along with the Diesel Oxidation Catalyst, Selective Catalytic Reduction and Ultra-Low Sulfur Diesel fuel work together to reduce carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM) and nitrogen oxides (NOx).

They do this by converting the pollutants into less harmful substances like carbon dioxide, water and nitrogen.

Why delete diesel emissions equipment?

If the diesel emissions equipment reduces the harmful pollutants making air safer for people with health issues and less harmful for the environment, why would owners want to remove aka delete diesel emissions equipment?

The simple answer is many see these systems as reducing the reliability of their diesel engines as well as reducing the performance of the engines in terms of power and fuel economy. For these owners, the truck is their livelihood and the emissions equipment causes them increased costs to operate their trucks as well as can cause increased repair time.

When faced with thousands in repair costs versus removing a part, many diesel truck owners opt to remove the part.

They also argue over the proposed scientific benefits of the emissions equipment and challenge the conclusions the equipment serves any benefit. Plus, if the U.S. Military and first responder vehicles get waivers to not use emissions equipment, why do consumers and commercial business have to use it? It all seems unfair to them.

Is deleting diesel emissions equipment illegal?

Now, the million dollar question. Did EPA Administrator Lee Zeldin’s new proposed rule rolling back the 2009 Endangerment Finding offer hope to diesel truck owners to legally remove the equipment? Experts say no.

The Speciality Equipment Manufacturer’s Association (SEMA) put out a statement on the proposed rule stating its focus on rolling back the EV mandate and offering more customer choices was a great move forward, however, it doesn’t change emissions rules.

In the statement, they provided a clear background statement on the EPA’s proposed new rule:

“The EPA’s proposed rule will directly impact federal new car requirements and does not impact existing emissions laws established by the Clean Air Act.”

Then, they added, “SEMA will review the proposed rule to identify any potential additional impacts to the specialty automotive aftermarket, even as the rule is not expected to impact Clean Air Act requirements related to the maintenance of emissions controls after a vehicle has been purchased.”

I reached out for further comment from SEMA and received this reply, “Based on our discussions with EPA, we expect this proposed rule to be specific to new vehicle requirements, with little specific impact to the aftermarket products that our members manufacture and sell. It’s not a policy that would rescind any ban on diesel defeat devices, for example. In that case, the law is 100% still the law.”

Allen Schaeffer, Executive Director, Engine Technology Forum, a long-time and leading advocate for advanced engine technology, including diesel engines, provided these comments in response to emailed questions.

“Regardless of what happens to this proposal from a legal challenge basis down the road….this action announced yesterday would NOT impact existing criteria emissions law for lead, ozone, particulates, nitrogen oxides, carbon monoxide, sulfur dioxide; EPA’s authority and duty to regulate these pollutants is well established in the Clean Air Act — which means that it would not impact emissions standards designed to reduce those emissions nor the technology we have today deployed to reduce those emissions – i.e. particulate traps and SCR systems, Schaeffer said.

Finally nothing in yesterday’s announcement makes tampering with emissions controls – removal, defeat devices, tuners, etc. legal.”

In the EPA’s announcement of the rollback, American Trucking Association President and CEO Chris Spear further dashed hopes of eliminating diesel emissions when he said, “The trucking industry supports cleaner, more efficient technologies, but we need policies rooted in real-world conditions. We thank the Trump Administration for returning us to a path of common sense, so that we can keep delivering for the American people as we continue to reduce our environmental impact.”

Our take

While diesel truck owners had high hopes the Trump administration would listen to their concerns, it seems they are still focused solely on the electric vehicle mandate and not going any further to really roll back the laws mandating the equipment they have found to be unreliable and detrimental to their businesses.

Unless something dramatically changes with President Trump’s administration, making deleting diesel emissions equipment legal is likely a lost cause for now.

This is/was their best shot in the past two decades to remove this equipment legally and unless the EPA or Congress decides to take further action changing the Clean Air Act law, it is hard to see anything changing.