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PRESENT-DAY cars are not capitalizing on the continued efforts of the petroleum industry to provide better fuels, the authors believe. The wide differences found in the octane-number requirements of individual cylinders, plus the failure to obtain uniform mixture distribution from cylinder to cylinder without resorting to fuels of aviation-grade volatility have led them to reach this conclusion, they explain. The probability that significant reduction in the average antiknock requirements of cars might be effected without making any major changes in the engine is indicated by a survey of the technical literature, they point out. The extensive studies of ignition-system characteristics and gasoline-mixture distribution as affecting detonation reported in their paper bring out the following pertinent points: 1. Variations actually occurring in the spark advance from cylinder to cylinder may vary the octane-number requirement of individual cylinders by about 10 points. 2.

PRESENT methods of correlating road knock behavior of fuels with laboratory methods are unsatisfactory and should be discarded in favor of a method that makes a new approach to the problem, the authors contend. Reviewing the causes of this situation, the paper offers evidence to show that the use of mathematical averages applied to the study of the car detonation problem has been very misleading and that the so-called average fuel octane-number requirement of existing cars and its corollary, the octane requirement of the average car, are values having little practical significance. A procedure is recommended by the authors as one approach to the problem of setting up a simple, practical way of evaluating fuels. It consists in selecting a number of privately owned cars and testing both reference-fuel blends and branded fuels in these cars without making any changes whatsoever in the engine adjustments. The results of two such surveys are reported.