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Increasing fuel costs and the desire for reduced dependence on foreign oil have brought the diesel engine to the forefront of future medium-duty vehicle applications in the United States due to its higher thermal efficiency and superior durability. One of the obstacles to the increased use of diesel engines in this platform is the Tier 2 emission standards. In order to succeed, diesel vehicles must comply with emissions standards while maintaining their excellent fuel economy. The availability of technologies-such as common rail fuel injection systems, low-sulfur diesel fuel, oxides of nitrogen (NOX) adsorber catalysts or NACs, and diesel particle filters (DPFs)-allows for the development of powertrain systems that have the potential to comply with these future requirements. In support of this, the U.S. Department of Energy (DOE) has engaged in several test projects under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity [1, 2, 3, 4, 5].

A 1991 Toyota Camry equipped with an electrically-heated catalyst (EHC) system was evaluated in duplicate over the Federal Test Procedure (FTP) with three different fuels. Evaluations were conducted with the EHC in place but without any external heating, and with the EHC operated with a post-crank heating strategy. The EHC system was placed immediately upstream of an original production catalyst, which was then moved to a location 40.6 cm from the exhaust manifold. The three test fuels were: 1) the Auto/Oil industry average gasoline, RF-A; 2) a fuel meeting California's Phase II gasoline specifications; and 3) a paraffinic test fuel. Non-methane organic gas (NMOG) emission rates with the EHC active were similiar with all three fuels, with absolute levels less than or equal to California's 50,000 mile Ultra-Low Emission Vehicle (ULEV) standard. Substantial differences, however were observed in the ozone forming potential of these fuels with the EHC active.