EPA Proposes Changes to Diesel Selective Catalytic Reduction Inducement Requirements

On Tuesday, July 14, 2026, the U.S. Environmental Protection Agency (EPA) proposed significant revisions to its diesel Selective Catalytic Reduction (SCR) inducement requirements, including requirements applicable to model year 2027 and later heavy-duty highway engines and vehicles. The proposal would move away from the current reliance on mandatory engine speed and power reductions—commonly known as “derates”—and place greater emphasis on warning systems and improved diagnostics to encourage proper diesel exhaust fluid (DEF) use and prevent emissions system tampering.

Under current requirements, vehicles may experience significant performance limitations when Selective Catalytic Reduction systems detect conditions such as low-quality or insufficient diesel exhaust fluid (DEF), component failures, or potential emissions system tampering. EPA is reexamining whether these performance restrictions are the least restrictive and most effective means of ensuring compliance.

As an alternative to the current inducement strategy, EPA is considering visual and audible dashboard warnings. The Agency cites research indicating that frequent and effective warnings can achieve high compliance while avoiding the operational disruptions and frustration associated with vehicle performance restrictions.

If finalized, the proposed revisions could represent a significant shift in EPA's heavy-duty diesel emissions compliance strategy. The approach would place greater emphasis on improving diagnostic accuracy, reducing false inducements, providing effective operator notifications, and maintaining emissions compliance without unnecessarily disrupting vehicle operation. Overall, EPA's proposal reflects an effort to balance emissions compliance with operational reliability and customer experience.

For the RV industry, the proposal could be particularly relevant to manufacturers and owners of diesel-powered motorhomes equipped with Selective Catalytic Reduction systems. Potential benefits could include fewer unexpected engine derates caused by sensor or component failures, reduced service disruptions, and lower warranty and diagnostic costs if false inducements decline. However, vehicle owners and operators would continue to be responsible for maintaining DEF systems and preventing emissions system tampering.

EPA published its proposal on July 14 for a 45-day comment period, expiring on Saturday, August 29. In addition, public hearings were held on Wednesday, July 29, and Thursday, July 30. For more information on the proposed rule, visit EPA’s website.   

The RV Industry Association will continue to monitor the proposal and engage where necessary as EPA evaluates how the proposed changes could affect future diesel-powered motorhomes and their owners. For more information about this issue, please contact Bill Erny, Senior Manager of Regulatory Affairs, at berny@rvia.org.