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The results of several anti-knock studies are discussed in this paper. Road anti-knock performance for 1000 fuel blends covering the years 1940 to 1957 have been investigated. The laboratory Research octane numbers of these fuels covered the range from 80 to 105. The fuels were evaluated in 46 cars representing a cross-section of the automotive products for these years. The objective of these investigations was to determine the practical application of the laboratory to road octane rating relationships, and the effect of vehicles, and operating conditions on these relationships. The results show that there is a valid correlation between laboratory and road octane ratings. The relative importance of Research and Motor octane ratings on road performance is influenced by make of car, engine speed, throttle position, and distributor advance characteristics. It also indicated that aromatics improve, whereas olefins reduce high speed Modified Borderline ratings.

The rapid trend in recent years toward higher octane fuels and high-performance engines has suggested a reappraisal of the ability of current laboratory knockrating methods to define the antiknock behavior of commercial gasolines in modern multicylinder passenger car engines. Road antiknock performance data have been obtained on 91 premium gasolines in five 1957 test cars and three cars equipped with experimental 11-to-1 compression ratio engines. In addition, 16 prototype gasolines were studied in the three high compression ratio cars. The data were analyzed by establishing a linear relationship between the road ratings and the laboratory data to determine the relative importance of each variable in enhancing the accuracy of the prediction equation. Of the many fuel laboratory variables, combinations of Research and Motor octane number, fuel composition and volatility were investigated as predictors of road performance.

Various investigators(1) have recognized that difficulties exist in obtaining octane ratings in the standardized single-cylinder laboratory CFR engine above 100 O.N. Efforts are being made by cooperative groups (such as ASTM) and individual laboratories to solve some of the problems. In the meantime, at the Sun Automotive laboratory, these developments have been paralleled by looking at the road rating problems using some “future design” experimental engines at a nominal 12:1 C.R. level. These engines were 1956 production engines of three different types modified to represent the high compression engine of a few years hence. The modified engines were installed in 1956 production cars. Recognizing that the ability of a petroleum refinery laboratory group to anticipate future engine design features is subject to some criticism, it was still felt that the results might well be helpful in defining future problems.