Four gasoline or gasoline-oxygenate blend fuels were used in the evaluation of regulated and unregulated emissions from five test vehicles. The fuels listed below were prepared from a common base gasoline.
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Baseline, aromatic-enriched (35.5% aromatics)
10% Ethanol blend (3.5% oxygen)
16.4% Methyl tertiary-butyl ether (MTBE) blend (3.0% oxygen)
19.1% Ethyl tertiary-butyl ether (ETBE) blend (3.0% oxygen)
The five test vehicles represented different types of emission control technology: pre-catalyst, oxidation catalyst, three-way catalyst with closed-loop carburetor operation and an air pump, three-way catalyst with throttle body fuel injection, and three-way catalyst with port fuel injection. Each vehicle was operated with each fuel over the Federal Test Procedure(1)* (including evaporative emissions) for a total of 15 tests per vehicle. Several unregulated exhaust emissions were measured including ethylene, 1,3-butadiene, isobutylene, benzene, toluene, o-, m-, and p-xylenes, formaldehyde, acetaldehyde, ethanol, MTBE, and nitrous oxide. The unregulated emission data from tests using the ethanol, MTBE, and ETBE blends were compared to emissions produced from tests using the aromatic-enriched baseline fuel to determine if there were any statistically significant differences associated with the use of the blends. Regulated exhaust emissions (hydrocarbons, carbon monoxide, and oxides of nitrogen) and fuel economy were also measured on each test. In addition, evaporative emissions were analyzed for MTBE, benzene, and ethanol.