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Octane requirements of late model vehicles were determined by trained knock raters and compared with those determined by customers. Average differences of independent distributions of customer and rater requirements were about 3 Research Octane Numbers/2 Motor Octane Numbers at part-throttle and 6 RON/4 MON at full-throttle and maximum octane requirement conditions. Five percent of the customers objected to knock when their cars were operated on fuel matching rater requirements, while 50 percent objected when using fuel 6 RON/4 MON lower. Another program is planned because differences between rater and customer octane requirements were greater than expected.

In late 1984 and early 1985, car owners in the Denver, Colorado area began complaining about driveability. All affected cars had port fuel injection systems. With time, complaints with certain makes of engines spread to other geographical areas. A test method was needed to study the factors causing flow- restricting deposits in the injectors. The Coordinating Research Council Automotive Fuel Injector Deposit Group was organized in March 1986. Within that group, a Test Procedures Subgroup was assigned the task of selecting a vehicle test procedure that related to field experience. Excellent cooperation between the automotive, petroleum, and supplier industries helped identify a test method that duplicated field experience involving injector deposits. This paper describes the CRC program to explore repeatability and reproducibility of the method.