The U.S. Environmental Protection Agency has announced a long-awaited fix to diesel exhaust fluid (DEF) regulations that, for years, have caused sudden and severe equipment shutdowns.

Administrator Lee Zeldin addressed the issue during his visit to the Iowa State Fair, saying farmers, truckers, and small businesses have endured millions in lost productivity due to unnecessary power derates in diesel engines. "It is unacceptable that these failures happen when they need equipment most," Zeldin said.

DEF is a urea-based fluid added to diesel exhaust streams to cut nitrous oxide emissions, a greenhouse gas the EPA says is 265 times more potent than CO. While effective for environmental compliance, the mid-2000s and early 2010s rules required trucks and heavy equipment to lose power or shut down if DEF levels ran out - a safeguard that often backfired when sensors failed, bringing machines to a crawl or a complete stop.

New Standards Start with 2027 Models

Under the new policy, diesel on-road trucks from model year 2027 will be designed so that running out of DEF will no longer cause sudden and severe power losses. For existing vehicles, the EPA has issued software guidance allowing manufacturers to reprogram systems to avoid crippling derates, reducing costly downtime during planting, harvest, and peak freight seasons.

Bipartisan Praise from Agricultural Advocates

Iowa Senator Joni Ernst welcomed the move, calling the old rules a "Green New Deal-type regulation" that literally brought tractors to a halt. "Not only will the new guidelines save family-run farms hundreds of millions every year, but it is also simply common sense," Ernst said.

According to Small Business Administrator Kelly Loeffler, the change is expected to save U.S. family farms about $727 million annually, offering a much-needed boost to rural economies still recovering from high input costs and volatile commodity markets.

Environmental Balance Remains in Place

While the new guidelines aim to protect productivity, they do not eliminate DEF systems entirely. Instead, they extend the grace period between a DEF failure and when a machine's power is reduced. This allows operators to finish critical work before addressing repairs - a compromise that maintains environmental standards without crippling operations.

The announcement follows recent EPA proposals to roll back certain greenhouse gas regulations, signaling a broader shift toward reducing regulatory burdens on U.S. agriculture and transportation while keeping core emissions controls intact.