Trump admin to eliminate DEF deratement

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”In the context of the X post you linked from Lee Zeldin (@epaleezeldin), who is the EPA Administrator in this 2026 scenario:

- **DEF** stands for **Diesel Exhaust Fluid** — a urea-based chemical injected into modern diesel engines to reduce harmful emissions (specifically NOx) as part of the Selective Catalytic Reduction (SCR) system.

- **Deratement** (or "derate"/"derating") refers to a **forced power reduction** (derate) that the engine's computer automatically imposes when the DEF system malfunctions, runs low on fluid, has a sensor failure, or experiences other aftertreatment/emissions-related problems. When a derate triggers:

- The engine significantly reduces available horsepower and torque (sometimes to as low as 5–20% of normal power, or even limp-home mode).

- This makes the vehicle (truck, tractor, heavy equipment, etc.) much slower, harder to operate, and often unsafe or impractical for work — especially for truckers on highways or farmers in the field.

- It is a deliberate EPA-mandated design feature in post-2010 diesel engines to force owners to repair emissions systems quickly and prevent tampering or defeat devices.

Lee Zeldin is describing a major pain point for diesel vehicle operators (truckers, farmers, construction, etc.) who face frequent, expensive DEF system failures and the resulting derates that cripple their equipment.

**What he is proposing/doing** (from the post): - In August 2025, he already issued updated **guidance** to engine manufacturers that reversed (or relaxed) some of these derate requirements. - Now, he's taking the next step: launching a formal **rulemaking process** to **permanently eliminate** these derates entirely.

- As part of building the case for that new regulation, he's sending a **mandatory data collection request** to manufacturers today.

This gathers detailed information on DEF system failure rates, patterns, costs, etc., so the EPA can independently evaluate the ongoing problems and justify removing the derate mandate.

In short, he's pushing a deregulation effort to get rid of what he (and many operators) see as overly punitive, unreliable, and burdensome EPA emissions enforcement mechanisms on diesel engines — aiming to make equipment more reliable and reduce downtime/repair costs for American truckers and farmers, at what he calls "Trump speed."

Replies to his post show strong support from that community, with many calling for even broader changes like fully removing DPF (Diesel Particulate Filter), SCR/DEF requirements, or allowing deletions after warranty.

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