Sensitivities of premium-grade gasoline have increased appreciably during the postwar years because refiners are limited in the ability to produce gasolines of high F-2 antiknock quality. Future gasolines are expected to have even higher sensitivities. Road depreciation of gasolines of varying sensitivity but similar research octane level has been determined in a variety of cars. Depreciation is significantly greater for more sensitive fuels, particularly at high engine speeds. The trend toward the use of automatic transmissions which raise the speed of maximum octane requirement will make sensitivity an ever increasing fuel liability. In order to utilize tomorrow's octanes effectively, the designers of future automotive engines must recognize this trend toward more sensitive fuels.