Over half of all Americans—about 156 million people—are exposed to unhealthy levels of air pollution each day. And diesel engines’ emissions are a big part of the problem. 

Thus, government agencies in various U.S. states, Canada, and the EPA of the United States, set regulations to limit the impact of these emissions. When implemented, the mandates reduce the volume polluting the air. 

Periodically, emissions rules are changed in response to new data, or to pursue enhanced clean air targets. In this guide, learn how the 2025 emissions rules impact commercial trucks, and how updates affect standard heavy-duty truck maintenance.  

How New Diesel Emission Systems Mandates Impact HDVs

Diesel emissions are the waste products created by burning diesel fuel. Most heavy-duty diesel vehicle emissions are released as exhaust. 

Diesel emissions systems mandates require heavy-duty vehicles to install filters, update engine mechanisms, and implement regular emissions testing (inspections)—all with the goal of reducing the total volume of exhaust pollution. 

Emissions Rules Overview: Updates & Changes 

Emissions regulations are periodically updated. 2025 brought a few notable changes to the trucking industry. 

2025 CARB Emissions Regulations 

The California Air Resources Board (CARB) made three changes to emissions regulations affecting heavy-duty truck operations in the state.  

Advanced Clean Fleets Regulation (ACF)

The ACF rules regulate state, municipal, and high-priority commercial fleets, as well as drayage trucks. 

These regulations require fleets to bring on zero-emission vehicles (ZEV). They set deadlines for the fleets to alter their composition, ensuring some percentage of medium- and heavy-duty trucks in a fleet be ZEVs by those dates. 

The most recent enforcement notice indicates enforcement actions targeting state and municipal fleets are the priority. Read CARB’s Advanced Clean Fleets Fact Sheet for more information.

Off-Road Diesel Fleets Regulation Update

The most recent updates to CARB’s Off-Road Regulation—which sets emissions parameters for commercial HDVs at mines, industrial logging sites, or construction sites (among others)—slightly modify 2023 and 2024 amendments. 

To reach emissions goals, CARB approved amendments to the Off-Road Regulation in 2024 and 2025. These include changes to phase-out dates for each model year (which differ by fleet size), and updated compliance deadlines. 

For amendment details and tables depicting clear deadlines, check out the CARB page “Overview of Amendments to the In‑Use Off‑Road Diesel‑Fueled Fleets Regulation.” 

CEPA & Transport Canada 

The Canadian Environmental Protection Act of 1999 (CEPA) is the roadmap for all environmental law and standards in Canada.

The legislation “Heavy-duty Vehicle and Engine Greenhouse Gas Emission Regulations” is the cornerstone environmental law regulating HDVs in Canada. While last amended in 2022, minor updates will affect the remainder of 2025, 2026 and 2027. These include:

• More flexibility and options for fleets to take advantage of the CO2 emission credit system

• Updates to GHG emissions limits checkpoints

• Changes bringing the CO2 emission standard (grams of CO2 per short ton-mile) for 2027 in alignment with CEPA Phase II

To delve deeper into these rules, read the official guidance document for Canada’s HDV GHG Emissions Regulations, published by the Ministry of Transportation. 

Proposed Changes To GHG EPA Emissions Standards 

Recently appointed EPA leaders have updated emissions rules, rolling back certain greenhouse gas (GHG) regulations for heavy-duty commercial vehicles.

Drivers and fleet managers can read about the changes to the rule on the EPA page “Final Rule: Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles – Phase 3.” 

How New Diesel Emission Systems Shape HDV Maintenance

Maintenance-specific FMCSA regulations are codified in Title 40, Part 1036–Control of Emissions From New and In-Use Heavy-Duty Highway Engines, in the section "Critical emission-related maintenance."

It includes two tables, which clearly list  the frequency at which each component of a truck’s emission system should be replaced or adjusted, per truck weight class. 

The tables were last amended in 2024.

Diesel Particulate Filter Maintenance & Green Tech

Often, new diesel emissions system technologies drive regulation amendments. Thus, the combination of the two most affects heavy-duty truck maintenance in practice. 

As both technology and law evolve and intersect, their combined impact can be seen in direct changes to the legal minimum system maintenance intervals, as DPF, EGR, and SCR models advance, and to best practices for optimization. 

New Rules Don’t Change Most Emissions Maintenance Best Practices

For the most part, regulation changes have only slightly altered the optimal process to maintain a heavy-duty truck’s EGR, SCR, and DEF tank. These include:

• Regular DEF quality checks, with NOx reduction monitoring

• Cleaning EGR filters, coolers, fuel injectors, and related parts every 50,000 miles

• Replace SCR-related crankcase ventilation valves and filters every 60,000 miles

• Clean DPF filters every 100,000 miles

• Replace DPF filter substrates every 650,000 miles 

For more detailed EGR and EPF maintenance guidance, check out our resources:

• Understanding Exhaust Gas Recirculation (EGR) Systems & Common Failures

• Common Diesel Particulate Filter Problems and What to Do About Them

2025 Clean Transportation Standards: Key Hurdles

New emissions standards pose a financial challenges.

Upfront Costs

The biggest financial hurdle is the cost of upgrading an older diesel truck, or purchasing a new low-emission / zero-emission HDV to comply with standards. A CARB report reveals “The average US/California zero-emission Class 8 truck in 2024 was priced at $435,839” while the average price of a comperable EV truck in Europe is “roughly $342,000.”

Incremental pricing for systems like the powertrain is also beyond what many independent operators and smaller fleets can afford up-front.

Compounding this, emissions regulations limit the resale value of diesel trucks. So, selling non-compliant HDVs in the fleet won’t free up as much cash for the new purchase as it might otherwise. 

OOS & Fines Penalize Poor Emission Compliance For Trucks

Fines and registration withholding are two of the most urgent penalties for heavy-duty trucks found non-compliant with regulations. 

According to the EPA, those found violating the Clean Air Act will be fined “up to $45,268  per noncompliant vehicle or engine, $4,527 per tampering event or sale of defeat device, and $45,268 per day for reporting and recordkeeping violations.”

However, some of those penalties are actually more costly in practice.

In some cases, the Federal Civil Penalties Inflation Adjustment Act Improvements Act of 2015 has increased the cost of penalties. For example, as of Fall 2025, a manufacturer violating the Clean Air Act may now be fined up to  $57,617 per violation, while any non-manufacturer tampering with emissions equipment (including “DPF delete”) faces penalties up to $5,761 per instance.

Registration withholding and mandatory out-of-service orders impose downtime on fleets. The costs of downtime can add up quite a bit. 

Meet Challenges With Incentives, Contracts & Fuel Savings

Fortunately, contemporary resources empower fleets to these challenges. 

Low Emissions / Zero-Emissions Contracts

Across Canada and 17 U.S. states, certain heavy-duty truck contracts are exclusively available to ZEVs. And, the percentage of ZEV-exclusive contracts will only increase with time. 

Tax Breaks & Grants

Many emissions regulations designed to usher in heavy-duty ZEVs come with incentives. These vouchers, grants, and tax breaks make compliance—including compliant maintenance practices—far more affordable. 

For example, Canada’s iMHZEV Program “provide[s] incentives of up to $200,000. Many different makes and models of eligible zero-emission vehicles for purchase or lease (12 months or more) are available to eligible organizations.” 

Similar, U.S.-based incentive programs include:

• California’s HVIP (Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project) 

• The U.S. EPA's Clean Heavy-Duty Vehicles (CHDV) Grant Program

• Grants provided through the Diesel Emissions Reduction Act (DERA) 

Moreover, in the long run, the reduced fuel and maintenance costs means a zero-emissions truck lasts longer and costs less per-mile than its diesel counterparts. 

Best Practices: Regulatory Compliance For Fleets

Mandates like the FMCSA’s Inspection Repair and Maintenance (Part 396) don’t always clarify the best way to comply. Fortunately, there are other organizations filling in those gaps. 

Regular, Frequent Inspection & Maintenance 

First and foremost, an HDV’s emission system should be maintained in accordance with the “Minimum Schedules Maintenance Intervals” detailed in Title 40. 

Drivers and fleet managers can use eCFR to view the section’s tables online. Each table clarifies the lowest legal intervals for cleaning, adjusting, repairing, or replacing emissions system parts. 

Optimize Inspections For Higher Compliance Rates

The HDV industry news and technology journal, Heavy Duty Trucking, offers fleet managers insights into optimizing driver inspections. Improved compliance is just one of many benefits. 

In the resource, “How to Get More Out of Commercial Driver Vehicle Inspections,” HDT emphasizes cultivating a culture of safety and compliance within a fleet. 

This starts with driver training, and it includes ways to lead by example, streamline the inspection process, and facilitate strong relationships between drivers and a trustworthy technician / service provider. 

Close Knowledge Gaps With Training

The FMCSA has been cutting away barriers to technician training—both for initial certification and ongoing compliance. 

As of March 2025, technicians can reduce “the federally required one-year of training or experience needed to conduct commercial vehicle inspections and brake-related repair and maintenance,” to 540 hours, “provided they received training based on TMC’s Recommended Practices.”

Emissions system maintenance training costs can also be offset by grants and scholarships through a wide range of programs, including:

• EPA’s Clean Heavy-Duty Vehicles Grant Program

• FMCSA's Commercial Motor Vehicle Operator Safety Training (CMVOST) program

• Department of Labor’s Workforce Innovation and Opportunity Act (WIOA)

• University partnership programs

A little knowledge is a powerful thing—even in the realm of fleet emissions compliance.

Advanced Technology To Monitor & Predict Problems

Implementing advanced technology can streamline all aspects of emissions compliance—from EDL recordkeeping to inspection to repair. Predictive analytics systems upgrade existing onboard diagnostics (OBD), empowering drivers to prevent damage to the truck’s emissions parts before it happens. 

Updates to technology also removes some of the tedious tasks from compliant processes. This makes them less burdensome, saving labor hours and increasing the life of a truck. 

Heavy-Duty Truck Maintenance In 2026 (+ Beyond)

As laws and technology advance, best practices for heavy-duty truck maintenance will continue to evolve. At Point Spring & Driveshaft Co., we’re ready.

No matter what your truck needs, we deliver service that works for you. To work with our commercial HDV specialists, call us at 888-787-7746. Or, reach out to our certified technicians by filling out the form below.