Starting today, engine makers can sell only heavy-duty truck diesel engines that meet the new EPA emissions standards: 2.5-grams oxides of nitrogen (NOx) plus non-methane hydrocarbon (NMHC). In 1998, six engine manufacturers signed a consent decree to produce engines meeting the new standards. Most of them will use cooled exhaust gas recirculation (EGR) to meet the levels, but Caterpillar chose to use its own Advanced Combustion Emissions Reduction Technology (ACERT) technology. Caterpillar has received conditional certification from EPA to sell on-highway truck engines after October 1. However, its engines still will fall short of new federal emissions standards, and Cat will be subject to fines for each one sold. Engines that meet the requirement will be commercially available beginning early next year. Unlike EGR technology, ACERT does not add exhaust gases to the combustion process, but rather relies on aftertreatment to lower emissions. Engine makers have tried to get the EPA deadline pushed back several times, most recently in July. The manufacturers say they haven't been given sufficient time to test new engines that cause less pollution and argued that the added cost of developing those engines will seriously harm an industry already reeling from years of declining sales. The next deadline for engine makers to clean their products comes in 2007. The regulations mandate that PM levels drop to 0.01 g/bhp.-hr., NOx to 0.20 g/bhp.-hr., and NMHC to 0.14 g/bhp.-hr. While PM standards will take effect immediately in 2007, NOx and NMHC levels will be phased in between 2007 and 2010.