EPA Proposes Killing Diesel Derate on New Engines, Hearing July 29

When does the EPA's proposed derate rule take effect?

The Environmental Protection Agency signed a proposed rule July 9, 2026, that would stop new diesel engines from cutting a truck's speed when the emissions system throws a fault. Instead of a derate (speed reduction), the driver gets a beep and a dashboard light. The rule applies only to new engines. EPA states it is "considering" guidance for the in-use fleet but has not published a timeline or mandate. A virtual hearing runs July 29 and 30, 2026, and written comments close Aug. 29.

The docket number is EPA-HQ-OAR-2026-0728. To testify at the virtual hearing, register by emailing [email protected] by July 22. The first session starts July 29 at 9 a.m. Eastern; the second runs July 30 at 10 a.m.

What the current derate rule does to your truck

Under the inducement rules at 40 CFR 1036.111, an engine must begin derating on a DEF (diesel exhaust fluid) quality reading outside the manufacturer's spec, or on open-circuit faults in the DEF tank level sensor, the DEF pump, the quality sensor, the SCR (selective catalytic reduction) harness, the NOx sensors, the dosing valve, or the tank heater. Any one of those triggers a derate. Not an emissions exceedance. A sensor. The regulation derates the truck for a broken wire.

The derate can drop a loaded truck from highway speed to 5 mph. EPA required manufacturers to develop this strategy in 2010. The agency now says its own mandate causes "needless frustration, operational delays, and real economic hardship." Those are EPA's words, published on its own website alongside the July 9 proposal.

Why EPA is reversing course after 16 years

EPA has carved out exceptions to the derate three times, each time acknowledging the safety risk. The agency exempted ambulances and fire apparatus from the derate in 2012 because a vehicle losing power en route to a trauma center was an unacceptable outcome. EPA is now proposing an emergency override for stationary and nonroad engines when human life is at risk. Tactical military vehicles can be entirely exempt from EPA emission standards under the national security exemption at 40 CFR 1068.225, with a companion provision that exempts the fuel they burn.

The July 9 proposal extends that logic to commercial trucks. EPA removed the DEF sensor requirement in August 2025, with savings EPA and the Small Business Administration jointly put at $13.79 billion a year. For one sensor.

What the proposal does NOT fix

The July 9 proposal covers new engines only. Millions of trucks use the old inducement logic in their ECUs (engine control units) today. EPA states it is "considering" guidance for the in-use fleet. Considering is not a plan. No deadline, no flash procedure, no funding mechanism has been published.

A presidential pardon reaches federal criminal punishment. It does not reach a civil judgment, a consent decree, or the statute itself. President Trump pardoned nine men July 3, 2026, who were convicted of defeating emissions systems. The pardons were for conduct the Justice Department will no longer prosecute. They do not repeal the Clean Air Act. Civil liability remains: $45,268 per tampered vehicle, $4,527 per defeat device sold, under current statute. California's Air Resources Board (CARB) operates under its own authority and budget and does not consult the DOJ's mood.

This is decriminalization, not legalization. The conduct stays unlawful. The federal posture becomes prosecutorial discretion, which can be reversed by the next deputy attorney general with a one-page memo.

The national security question EPA has not answered

Roughly 90% of Defense Department domestic freight moves on commercial carriers, on commercial equipment, under commercial contracts, driven by commercial drivers. Deployment does not fail at the port. It fails on the road to the port, at scale. The tactical vehicle sitting on the flatbed is exempt under 40 CFR 1068.225. The tractor pulling the flatbed is not. It will drop to 5 mph in a live lane during a surge because a $200 sensor decided the urea concentration was wrong.

The most serious threat to American trucking is not the criminals. It is written into the Code of Federal Regulations, which anyone could have read. A federally mandated speed derate on a live interstate is a highway safety issue. FMCSA (Federal Motor Carrier Safety Administration) writes the out-of-service criteria, and no one has ever asked whether a mandated derate constitutes a vehicle defect.

What small fleets need to do before Aug. 29

Every fleet manager, every owner-operator, every rural fire chief, every farmer who has watched a tractor drop to a crawl in a harvest window has standing to speak into the docket record. The record is the only thing that survives an administration.

Three things would finish the fix. First, kill the derate outright, for every engine, in use and new. The July 9 proposal covers new engines and states that EPA is "considering" guidance for the in-use fleet. Order the fix, fund the flash, set a deadline. Second, release the warranty data. EPA demanded aftertreatment warranty data in February 2026, and 11 of 14 manufacturers submitted it. Publish the line item the American Transportation Research Institute cannot get and the OEMs will not give. Third, answer the national security question. Somebody with subpoena power should ask why 40 CFR 1068.225 exempts the tactical vehicle and not the commercial tractor that carries it.

To testify at the virtual hearing, register by emailing [email protected] by July 22, 2026. Written comments close Aug. 29. The docket is EPA-HQ-OAR-2026-0728. If you run a small fleet and you have ever lost a load, missed a delivery window, or pulled onto a shoulder at 5 mph because a DEF sensor faulted, put that in the record. The agency is asking. Answer.