On February 7 and 8, Mack Trucks Inc., Volvo Group North America LLC, Daimler Trucks North America LLC, and Detroit Diesel Corp. filed petitions for review in the U.S. Court of Appeals for the District of Columbia Circuit challenging the Environmental Protection Agency’s interim final rule that specifically allows Navistar Inc. to pay nonconformance penalties in order to continue producing heavy-duty, 2012 and 2013 model-year diesel engines that exceed nitrogen oxides limits. The plaintiffs use liquid, urea-based selective catalyst reduction technology, whereas Navistar uses exhaust gas recirculation technology to control nitrogen oxides emissions from its engines. EPA is allowed to accept nonconformance payments from a manufacturer if three conditions exist; the standard has become more difficult to meet; significant work is required to comply; and technological reasons account for nonconformance. The agency will accept comments on the rule until April 14.