You know all those Biden-era Greenhouse Gas standards and Environmental Protection Agency (EPA) mandates regarding emissions standards for light- and medium-duty vehicles set to take place beginning with model year 2027? Or (and perhaps closer to the heart of the trucking industry) those looming deadlines for emissions regulations on heavy-duty vehicles?
For months, the trucking industry has been formulating a plan to deal with the threatened 2027 model-year regulations on emissions and fuel efficiency, with some carriers planning to pre-buy, or purchase larger numbers of 2025 and 2026 model-year tractors in an effort to reduce purchases of 2027 models. The idea is to let others deal with the technological changes and the increased costs of maintaining them. Another large incentive for pre-buying is the federal requirement to extend the useful life of the vehicles produced, addressable with longer vehicle warranties that increase the purchase price by as much as 30%.
“But wait — not so fast!” says the new leadership at EPA, appointed by the Trump administration.
On March 12, 2025, EPA Administrator Lee Zeldin announced that the emissions rules mandated under the Biden administration were being reviewed. The action began weeks earlier, however, with a stack of executive orders issued by incoming president Donald Trump on his first day in office.
In a story penned for the Wall Street Journal, Zeldin said, “We are driving a dagger through the heart of climate-change religion and ushering in America’s Golden Age.” He also wrote, “This isn’t about abandoning environmental protection — it’s about achieving it through innovation and not strangulation.”
Rolling it all back
Zeldin’s comments come as the EPA works to roll back 31 separate environmental rules put in place under the Biden administration. The regulations include those in place on electric power plants and restrictions on the oil and gas industry as well as reconsideration of light-duty, medium-duty and heavy-duty vehicle regulations and NOx standards.
A key rollback attempt will address the 2009 finding by then-EPA administrator Lisa Jackson that greenhouse gases in the atmosphere “threaten the public health and welfare of current and future generations.” The same action included a finding that greenhouse gases from motor vehicles contribute to greenhouse gas pollution.
These findings were the basis for a number of EPA actions on the automotive and trucking industries to increase efficiency and reduce GHG emissions.
Greenhouse Gas Emissions Standards
The EPA’s “Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles – Phase 3” final rule was published March 29, 2024. It specifies that heavy-duty trucks must achieve a reduction in carbon dioxide emissions beginning with the 2027 model year for vocational trucks and expanding to sleeper-equipped tractors by 2030. By 2032, the specified reductions are 30% for vocational trucks, 40% for day cab tractors and 25% for sleeper tractors.
Another EPA final rule, “Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards,” was published on Dec. 20, 2022. New emissions guidelines were announced by the agency that would cut nitrous oxide emissions by 48% by the year 2045. The ruling also included longer “useful life” requirements that would likely force manufacturers to lengthen warranty periods on new vehicles, driving up the cost by as much as 30%.
The GHG rules might be achievable through greater fuel efficiency — and perhaps by smaller diesel engines.
The NOx ruling would require redesign of engines and more robust aftertreatment systems. One consideration is that aftertreatment systems are more effective at higher temperatures. Higher combustion temperatures can be achieved with piston redesign and other modifications, but engines that are idling or operating under low-RPM conditions may not be able to maintain high enough temperatures.
The inevitable bugs
As with any new technology, there are inevitably bugs that must be worked out before full public acceptance is gained.
Many in trucking clearly remember the issues around the 2007 model-year diesel engines in which mufflers were replaced with particulate filters.
The filters would collect carbon particles from the diesel exhaust, which was then burned off through a regeneration process that used diesel fuel for ignition. The unproven technology was undependable, often leaving drivers on the side of the road with plugged particulate filters that needed replacement to make the truck operational again.
Not only did those 2007 model-year trucks cost more … they also required more fuel to operate.
… and then along came DEF
The next phase of EPA regulation of diesel engines took place with the 2010 model-year, when Selective Catalytic Reduction (SCR) was introduced.
The population was already familiar with catalytic converters, which had been installed on gasoline-powered automobiles for decades. Now heavy-duty trucks had converters too, with one very large difference: Whereas gasoline converters were passive — they worked without additional additives — SCR converters needed the injection of a chemical to work properly.
The industry was introduced to Diesel Exhaust Fluid (DEF), a name that sounded suspiciously like the “blinker fluid” or “horn lubricant” jokes often heard among motorists. DEF was real, however, and drivers became accustomed to having another tank to top off on their trucks.
The increased aftertreatment required by the EPA’s NOx mandate may require heavier use of DEF to reach emissions goals, or even the addition of another SCR to each vehicle.
Engine oil changes also on the horizon
Another change that is coming to trucking is in the formulation of engine oils. Newer engines will run hotter, and they’ll have closer tolerances that require a thinner oil. Many trucks currently use oil classified by the Society of American Engineers (S.A.E.) as CK-4.
As lubricant requirements changed, “backwards compatibility” was engineered into each. This meant that CK-4 oils will work in engines that were designed back when oils were CJ-4 or even CH-4.
The newer oil category, FA-4, may not be compatible with older engines. Whereas older oils might have a viscosity range of 15-40 or higher, FA oils are thinner to allow for closer tolerances between engine parts and might be 5w-30 or similar.
Still up in the air
Exactly where the Trump-ordered EPA revisions will end up won’t be known for a while.
Changes to existing regulations must undergo the usual federal agency rulemaking process with a notice of proposed rulemaking followed by a period for public comment and a final rule, all published in the Federal Register. It’s possible that Congress could pass legislation that shortens the process, but presidential executive orders aren’t enough to eliminate the rules already enacted.
Whether current efficiency and emissions rules will be delayed or completely scrapped will be revealed in the coming months.
Cliff Abbott is an experienced commercial vehicle driver and owner-operator who still holds a CDL in his home state of Alabama. In nearly 40 years in trucking, he’s been an instructor and trainer and has managed safety and recruiting operations for several carriers. Having never lost his love of the road, Cliff has written a book and hundreds of songs and has been writing for The Trucker for more than a decade.
