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. About half of the drivers indicating unsatisfactory performance had fuel injected vehicles. Vehicle hesitation was the most common malfunction associated with driver dissatisfaction.