EXPERIMENTS carried out in 1930 by the Knock Rating of Motor Fuels Subcommittee of the Institution of Petroleum Technologists are described in the paper which, in reality, is a continuation of one presented at the 1930 Annual Meeting of the Society. Various fuels, both straight run and blended, were tested in the Ricardo 2-liter E-35, the Delco and the Armstrong engines under three different sets of conditions and were rated in terms of blends of a high-value and a low-value straight-run gasoline, benzene and heptane and iso-octane and heptane. The last method gave a greater degree of fluctuation in knock intensity than the benzene-heptane blend, and in the future all knock ratings will be expressed in terms of the octane number, which is in agreement with knock-rating practice in the United States.
