If you are a diesel vehicle owner, then listen up. Under EPA´s earlier regulations, if DEF sensors detected poor fluid quality, or if the sensor itself malfunctioned, the vehicle´s engine would "derate," limiting speed or forcing a full shutdown of the engine to ensure emissions compliance.

The EPA´s regulatory shift may affect DEF demand. The switch to NOx sensors implies a certain level of allowable dilution of urea concentration in the DEF supply in selective catalytic reduction (SCR) systems, which could reduce DEF consumption in both on-road and off-road applications.

What does that mean for owners? Now, under the new regulations, when the DEF system sensors fail or go out of range, no longer will the vehicle derate to 15 MPH. The EPA said it will issue a new deregulatory proposal to completely remove all DEF deratements for new diesel engines.

The agency will continue to monitor these developments and will engage with the agency as the rulemaking process unfolds. Happy Motoring.