Driveability Index and Driver Satisfaction with ETBE and MTBE Gasolines at Intermediate Ambient Temperatures

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.