In the past six months the second Trump administration has launched an unprecedented assault on a whole slate of diesel exhaust emissions regulations.

Diesel exhaust regulations, drafted by the California Air Resource Board (CARB) and the U.S. Environmental Protection Agency have dominated the trucking industry for decades now. 

Over the past 20 years or so, these regulations have reduced diesel exhaust emissions to levels that were once thought impossible to achieve. 

Today’s diesel engines are the cleanest in history.

On top of the tailpipe emissions regulations, greenhouse gas emissions have been targeted at both the federal level and by CARB, essentially forcing trucking fleets to move toward new, zero-emission powertrain solutions that are currently more expensive to purchase than diesel trucks and not workable in many applications.

These systems have given fleets exasperating teething problems at times. And they have helped drive the price of new diesel-powered trucks up considerably over the years.

Confusing, Complex and Confounding Regulations

The various emissions regulations heading into 2027, issued by two separate government agencies, were also complex and confusing. And they pushed fleets to adopt new, zero-emission powertrain solutions that are currently more expensive to purchase than diesel trucks. And they do not perform as well as diesel trucks in some applications.

But of all those regulations, EPA’s 2027 Heavy-Duty Engine and Vehicle Standards were among the most dreaded by the trucking industry.

Beginning that year, diesel trucks were slated to receive a serious influx of new emissions reduction technologies combined with extended warranty requirements for exhaust aftertreatment systems.

Moreover, price increases associated with those technologies and new components were projected to raise the price of 2028 Class 8 trucks by as much as $25,000 per vehicle.

Which is why the Trump administrations regulatory rollbacks have been greeted warmly by the U.S. trucking industry.

As of June, EPA 2027 technically remains in effect. However, the Trump administration has made it clear that intends to “revisit” these standards. Given its other recent actions revisiting or rolling back both EPA and CARB diesel exhaust and Greenhouse Gas emissions regulations, it is generally assumed that significant, trucking-friendly changes to EPA 2027 are coming.

However, no one knows for sure yet what the Trump EPA will do.

Will EPA toss the rule entirely? Or will they choose to retain some elements of the regulations?

All of this has created a great deal of uncertainty in the North American trucking industry.

Prior to Trump’s reelection it was generally assumed that a massive Class 8 prebuy would kick off sometime in 2025. It seemed logical that fleets would move to acquire new trucks before the sharp 2027 price increases took effect.

That prebuy hasn’t happened yet, for a variety of reasons. Although the prevailing belief OEMs will no longer be required to offer new trucks with some, or all of the components and warranty extensions mandated by EPA 2027 has definitely contributed to a “wait and see” approach for many fleets. 

On the other hand, truck OEMs have invested billions of dollars in new diesel emissions technologies. And those OEMs, understandably, want to recoup those investments as soon as possible.

And – again – no knows what the Trump EPA will eventually decide in regard to the 2027 diesel emissions regulations. 

Which means that no one is certain what Class 8 OEMs will do with their 2027 model year trucks in terms of technology or warranty extensions. Or what any of this means in terms of pricing heading into 2027.

Uncertainty Across the Board

In short, the Class 8 truck market is currently a chaotic mess heading into 2027.

To try and gain some clarity as to where things stand – and are liked headed – HDT reached out to Brian Antonellis, senior vice president of fleet operations for Fleet Advantage.

And he absolutely agrees that the industry has been on a wild roller coaster ride over the past few months with regard to new 2027 trucks.

With the death of CARB’s Advanced Clean Fleets, Antonellis said fleets naturally assumed that since the enforcement arm that would charge penalties for noncompliance had been removed, they’d be able to do what they want with regard to spec’ing new trucks and acquire new trucks when and where they are needed.

Next, to fall was CARB’s Advanced Clean Truck rule (ACT), which was nullified in May. 

And that was a real win for truck dealers, Antonellis said. 

“I know there are still some legislation and court challenges remaining for ACT,” he says. “But this still makes it easier for dealers to sell diesel trucks in California.”

But the really big blow, Antonellis says, was the nullification of CARB’s Omnibus Low-NOx regulation. 

Like EPA 2027, the Omnibus low-NOx regulation was aimed at reducing diesel exhaust emissions. In essence, the Omnibus rules became law in CARB states beginning 2024. In many ways they were a precursor the EPA 2027, which would effect fleets nationwide beginning in January of that year.

CARB Omnibus and EPA 2027 required diesel engine manufacturers to reduce diesel exhaust emissions by 90%. They also required OEMs to extend the useful life of heavy-duty diesel engines from 435,000 miles to 650,000 miles and increased warranties from 100,000 miles to 450,000 miles for exhaust aftertreatment systems.

Higher Prices – Lower MPG

In practice, however, Antonellis says nullification of the Omnibus rule really only affects fleets between now and 2027. That’s because, as noted, the EPA 2027 diesel emissions mandate still stands.

“Rescinding the Omnibus rule means that EPA isn’t going to be able enforce it before 2027 in the 14 CARB states,” he explains. “Although we still don’t know what’s going to happen with EPA 2027.”

Without the regulatory pressure from CARB states Antonellis thinks OEMs are likely to shelve the aftertreatment warranty extensions required by EPA 2027. But he also thinks the OEMs will move ahead and put new Omnibus-EPA 2027 compliant diesel engines in Class 8 trucks beginning that year.

“I think you're going to see the cost of the new engines increase probably between $8,000 and $10,000,” he says. “That’s the average upcharge for an Omnibus-compliant engine in CARB states, today.”

And, Antonellis adds, if the freight market improves somewhat over the next 12 to 18 months, that price increase could still spark a modest pre-2027 Class 8 prebuy.

Another factor that has to be considered, Antonellis adds, is that some indications project that fuel economy on 2027 model trucks will be slightly worse than current models.

That’s because OEMs are increasingly likely to switch to 24-volt electrical systems to get aftertreatment systems hotter for more efficient PM and NOx burns.

“Volvo took the lead on going to a 24-volt system,” Antonellis says. “International hasn’t done so yet – but they’re signaling they might have too as well. Even Cummins is going back and forth on whether they’re going to need to go to a 24-volt system. And if the trucks go to 24-volt systems, they’re probably going to lose fuel economy.”

“I think that price increase and the possibility of reduced fuel economy will drive some additional purchasing activity in 2026,” he says. “It won’t be the massive prebuy everyone thought was going to happen. But I do think there will be a strategic prebuy in Q3 and Q4 of 2026, similar to what we saw back in 2012.”