Fleet Impact Summary – EPA 2027 Low NOx Diesel Regulation

What Is EPA 2027?

EPA ’27 signifies the latest advancement in diesel engine technology to significantly reduce nitrogen oxide (NOx) and particulate matter (PM) emissions for new on-highway diesel engines beginning January 1, 2027. Unlike other recent regulations, such as California’s Advanced Clean Fleets (ACF) initiative, EPA ’27 does not require fleets to adopt ZEVs.

What the EPA Has Confirmed and Proposed

Confirmed:

• 2027 NOx standard will remain at 35 mg (0.035 grams), 82% lower than the 2010 standard.

Proposed:
The EPA announced its proposed revisions on July 14, 2026, which include modifications to the following areas of the original regulation:

• Current Warranties Kept: The proposal cancels the planned jump to a 10-year/450,000-mile warranty. It keeps today’s 5-year/100,000-mile emissions warranty.
• Useful-Life Delay: Rules extending how long an engine must prove its emissions compliance are delayed until model year 2030. Engines from 2027 to 2029 will use current standards.
• Nonconformance Penalties (NCP): OEMs that cannot meet the 2027 limits right away can pay a temporary fine per engine to keep products on the market without causing severe supply shortages.
• DEF Derates: Mandatory engine power reductions or vehicle speed derates tied to Diesel Exhaust Fluid (DEF) issues would be removed and replaced by visible or audible dashboard warnings.

What That Means for Fleets

• • MD / HD diesel-powered trucks will cost more. Based on the proposed changes, which we anticipate will be adopted in the near future, industry estimates a minimum increase of $4,500 for MD and $7,000 for HD chassis options. Actual cost increases will depend on OEM guidance and the final 2026 EPA proposal.
  • Order allocation for MD / HD chassis is limited. Due to the uncertainty leading up to this regulation, in addition to large trucking fleets pre-ordering chassis early this calendar year, OEMs have limited to no build slots for pre 2027 engine model year units.

Risks to Monitor

1. Pricing Uncertainty: Final EPA ’27 engine pricing cannot be fully known until the 2026 rule adjustment proposal is released; interim volatility should be expected.
2. Production Allocation Pressure: Limited production availability has driven up the base cost for most, if not all, MD/HD OEMs, further increasing the cost of new MY trucks. Pricing may adjust as the new regulations and emissions technology go into effect.
3. Technology Integration:

• • • • ’27 MY diesel engines, 12L and larger, are already EPA ’27 certified.

• • • • • Most diesel engines less than 12 liters are still not EPA certified and, until further notice, will be subject to the Nonconformance Penalty.
          • There is no clear projection of how long the EPA will allow NCP to be used before new technology is required (EPA ’27).

Looking Back: How We Got Here

U.S. NOx-reduction efforts began in the 1970s as emissions were linked to ground-level ozone, air-quality degradation, and adverse health effects. Major diesel-engine milestones follow:

• • • • EPA 2010 engines targeted a 75% NOx reduction to 0.2 grams and remained in place for approximately 15 years.
      • In 2021, CARB’s Low NOx Omnibus rule reduced the standard by an additional 75% (0.05 grams) beginning in 2024.
      • The Clean Truck Partnership between CARB, OEMs, and the EPA established a nationwide 0.035-gram standard for 2027, now referred to as EPA ’27.

Looking Forward: Recommended Fleet Actions

Start planning now. Understanding what limitations may currently be in place for each OEM will be essential to minimizing order disruptions and improving fleet communication. Fleets should:

• • • • • Engage OEM partners early to understand build-slot availability, allocation risk, and platform changes.
        • Review vocational upfit compatibility and electrical requirements as engine designs evolve.
        • Evaluate potential alternative fuel solutions in lieu of diesel options.

While EPA ’27 introduces cost and other considerations, fleets should also recognize that cleaner diesel technology remains a viable pathway to meet required government emissions reduction goals when compared to full fleet electrification mandates. Other alternative fuel solutions may be available that deliver both emissions and cost savings. For now, Holman will continue to monitor regulatory developments and advise fleet customers as additional guidance becomes available.