Proposed Rule: Amendments and Nonconformance Penalties for Model Year 2027 and Later Heavy-Duty Highway Engines and Amendments to Inducement Provisions for SCR-Equipped Diesel Engines
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Rule Summary
On July 9, 2026, the U.S. Environmental Protection Agency announced proposed regulatory amendments to certain compliance provisions and test procedures related to model years 2027 and later heavy-duty highway engines. These amendments would include changes to the regulatory useful life periods and the emission-related warranty periods. EPA also proposes to add clarity to certain regulatory compliance provisions and correct errors in the regulations to support the model year 2027 and later program for heavy-duty highway engines and vehicles. This includes certain amendments related to provisions adopted in January 2023 as well as other provisions adopted in earlier rules. EPA also proposes to make nonconformance penalties available to manufacturers of medium heavy-duty engines and heavy heavy-duty engines beginning in model year 2027.
In addition, EPA proposes to amend the inducement provisions for selective catalytic reduction systems that use DEF. The proposal would replace the requirement for engine derates and vehicle speed reductions with audible and/or visible notifications for newly manufactured diesel-fueled highway engines and vehicles (i.e., light-duty and medium-duty vehicles and heavy-duty engines) and nonroad engines and equipment. EPA is also considering a process to issue updated guidance that would allow manufacturers to modify in-use engines and vehicles, consistent with any changes that the Agency adopts for certifying new engines and vehicles.
Documents Related to this Proposal
- Notice of Proposed Rule (pdf)
- Draft Regulatory Impact Analysis (pdf)
- Draft Technical Support Document, Nonconformance Penalty (pdf)
Comment and Public Hearing Information
Public hearing details and public comment opportunity.