Further Analysis of the Effects of Heavy Aromatics and Ethanol on Gasoline Road Octane Ratings

A Road octane study conducted by the Coordinating Research Council showed heavy aromatics in gasoline to have a small adverse effect on Road octane number; but ethanol content, which was also evaluated, was not found to be a significant factor. In this paper, the data are analysed further by introducing car design variables in addition to heavy aromatics, ethanol, and the two laboratory engine octane tests. This analysis shows 10% ethanol in gasoline to have a small but beneficial effect on Road octane number independent of laboratory octane quality. The average effects in the two analyses were nearly identical, but the statistical significance of the effects differed.