EPA seeks removal of diesel emissions equipment from trucks

A new EPA memo is circulating around the agency aimed at rolling back a landmark finding critical to climate change rules, which would remove diesel emissions equipment from trucks as well as have other massive changes. Here’s what we know so far.

EPA seeks removal of diesel emissions equipment 

The draft memo, as reported by many news organizations, states the EPA is seeking to undo the 2009 Endangerment Finding, which is the backbone of climate change rules centered around Greenhouse Gas emissions. This idea was first brought up on March 12, 2025, when EPA Administrator Lee Zeldin declared the greatest day of deregulation for the agency. 

He pointed to the 2009 Endangerment Finding as one item in particular they were looking at undoing.

What is the 2009 Endangerment Finding?

The 2009 Endangerment Finding was part of the outcome of the landmark 2007 Massachusetts v. EPA case. 

That U.S. Supreme Court case forced the EPA to start to regulate GHG emissions since the state of Massachusetts was able to prove those gases were causing damage to the health and welfare of their citizens and their industries, like fishing, through the rising water temperatures. 

After the ruling, the EPA issued the 2009 Endangerment Finding declaring 6 greenhouse gases (CO2, methane, nitrous oxide, HFCs, PFCs and SF6) threatened both public health and welfare.

This finding was added to the Clean Air Act and subsequent rules were put in place regulating these gases for transportation industries as well as other industries like power plants. 

Why is diesel emissions equipment controversial?

What this finding did was force all automakers to quickly develop emissions equipment for diesel engines to reduce greenhouse gases from the atmosphere. 

This also led to the creation of low sulfur diesel fuel and diesel exhaust fluid in the United States as well as several other parts of the world. 

The speed of developing these systems led to reliability issues right off the bat. Initially, the first diesel engine trucks saw a significant decrease in performance, fuel economy and when, not if, these systems failed, the costs to repair them were astronomical. Many owners simply unbolted the systems and tossed the equipment in the trash.

Over the past two decades, diesel trucks have improved along with the diesel emissions equipment. Engine performance and fuel economy have surpassed the pre-emissions diesel trucks and reliability has become better. 

However, it is hard for many truck owners to trust the new trucks after being burned so badly in the past on the high repair costs on the older trucks.

What if it is reversed?

If the 2009 Endangerment Finding is reversed, the EPA will no longer be required to regulate greenhouse gas emissions. This will remove the need for diesel emissions equipment.

Automakers are already prepared to build trucks without the diesel emissions equipment — like they do for U.S. combat vehicles serving in overseas locations without access to low sulfur diesel fuel. 

And there are delete kits readily available for sale that are so far illegal to install in the U.S. This could change overnight as well.

Our take

Can this key landmark finding be reversed so easily? The simple answer is no. Without digging into the weeds on how things work in Washington, the fact is the EPA would have to prove: The facts in the Endangerment Finding report weren’t accurate; the fisheries in Massachusetts were not impacted by GHG; and the U.S. Supreme Court ruled incorrectly. 

Then, the EPA would need Congress rewrite the law since the overturning of the Chevron Doctrine means the agency can’t do it itself.

And the EPA, Congress and the courts have to decide if the fishing industries — and other industries such as farming, ranching, etc. — needs outweigh diesel truck owners and transportation companies concerns over reliability and repair cost concerns on diesel emissions equipment.