In a move welcomed by rural America, the U.S. Environmental Protection Agency has announced new guidance that relaxes rules around diesel exhaust fluid systems, better known as DEF. This change promises smoother hauling and field work for farmers and truckers alike.

According to DTN’s coverage of the announcement on August 12, 2025, the EPA is allowing software tweaks to existing vehicles so they no longer suffer sudden slowdowns or shutdowns when DEF runs out or a system sensor fails.

Currently, when a DEF system glitch occurs, vehicles are often forced to crawl along at only five miles per hour within a few hours. That can grind agribusiness and transport logistics to a halt. The new guidance gives the industry more time to act. Instead of an immediate performance hit, the system now allows up to 650 miles or 10 hours before even triggering a warning light. For one full day, vehicle performance remains unaffected. After that, operations continue, but with roughly a 15 percent engine power reduction rather than crippling slowdowns. In fact, vehicles can still operate normally for up to 4,200 miles (that is about two extra work weeks) before speed is limited to 25 miles per hour. That will only happen after around four weeks without repair or DEF replenishment.

EPA Administrator Lee Zeldin acknowledged the widespread frustration: “It is unacceptable that farmers, truckers, construction workers and many other small businesses continually experience failures of diesel powered equipment when they need it most.” Secretary of Agriculture Brooke Rollins added that the new guidance “will allow our agricultural producers to spend more time in the fields than in the repair shop,” calling it a common sense fix to an overly restrictive regulation.

AgWeb’s reporting highlights that this is part of an effort to cut regulatory red tape for manufacturers of farm machinery and heavy-duty vehicles. The article reports that Small Business Administration (SBA) leader Kelly Loeffler claims that the new rule will result in 1.8 million family farms across America saving a staggering $727 million per year while offering “vital financial and operational certainty.”

Why This Matters for Farmers

• Less downtime, more productivity: The threat of sudden stoppage due to DEF issues has been a significant headache. Now, with a buffer period built in, equipment can stay active longer even during DEF failures or sensor malfunctions.
• Simplified repairs: Allowing software-based solutions to current vehicles removes the need for lengthy bureaucratic approval, something that often keeps machinery grounded longer than necessary.
• Peace of mind on the road and in the field: Whether towing grain trailers across the country or navigating fields with tractors, operators can now count on machinery that keeps moving until they can safely address the DEF situation.

This latest guidance from the EPA makes clear its intention to better support the needs of farmers, truckers, and agricultural equipment operators, letting them focus more on work and less on red tape or unexpected breakdowns.

Many farmers see this policy shift as a welcome first step, but are hoping it signals a larger move toward eliminating DEF systems entirely. Since their introduction more than a decade ago, these systems have been a constant source of frustration in the ag community, adding maintenance headaches, unexpected downtime, and extra costs to already tight operating budgets. While supporters of DEF point to its emissions benefits, many producers argue that the complexity and expense outweigh the gains. For them, the ultimate goal is not just fewer restrictions, but the freedom to operate the most efficient machinery possible.