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Aromatics, cetane number, density, and lubricity of a large number of retail diesel fuel samples were compared before, during, and after the switch from low sulfur to ultra low sulfur diesel fuel. Also, sulfur and nitrogen speciation was done on a small set of samples to determine the changes in heterocyclic compounds as refiners made the switch. For ultra low sulfur fuel, total aromatics decreased substantially, density decreased slightly, cetane number increased by about 1 - 2 numbers, and lubricity (wear scar) improved slightly relative to low sulfur diesel fuel. Speciation results showed that hydrotreating eliminated thiophenes and benzothiophenes from the fuel. The only sulfur species remaining were dibenzothiophenes, and these were present at very low part per million levels. Nitrogen compounds in the form of carbazoles were either eliminated or reduced to low part per million levels.

Driver satisfaction with cold start and warm-up driveability of low vapor pressure gasolines as a function of Driveability Index was studied during intermediate ambient temperatures. The gasolines had a vapor pressure of 55 kPa (8 psi) and contained nominally 2.7 mass percent oxygen as either 15 volume percent MTBE or 16 volume percent ETBE. Driver questionnaire responses were used to measure satisfaction with each fuel. The results show that as DI increased, driver satisfaction decreased in a nonlinear manner. At the same DI levels, driver satisfaction with 16% ETBE fuels was similar to that with 15% MTBE fuels. Statistical analysis of the responses showed that satisfaction with ETBE fuels was dependent on fuel delivery system while with MTBE fuels, satisfaction was independent of fuel delivery system. Hesitation and sluggishness were the most common malfunctions associated with dissatisfaction.

The effects of Driveability Index (DI) and methyl tertiary butyl ether (MTBE) on driver satisfaction with nominal 9 psi gasolines at intermediate ambient temperatures (30-50°F) were studied. Test fuels were nominally premium octane and consisted of five all-hydrocarbon fuels of varying DI (1187-1320°F) and five 15% MTBE fuels (1088-1242°F) splash blended from the all-hydrocarbon fuels. Forty one drivers completed both fuel series. Vehicle model years represented were 1977-1992. Driver questionnaire responses were used to measure satisfaction with each fuel. Results show that as DI increased, driver satisfaction decreased. Splash blended MTBE fuels had higher driver satisfaction than the parent all-hydrocarbon fuels. At the same DI level, however, all-hydrocarbon fuels provided higher driver satisfaction than 15% MTBE fuels. To achieve the same satisfaction level as an all-hydrocarbon fuel, a 15% MTBE blend needed a DI that was from 54 to 64°F lower.