Octane Requirement Increase in 1971 Model Cars with Leaded and Unleaded Gasolines (Report of a Pilot Program of the Road Test Group of the Motor Vehicle Fuel, Lubricant, and Equipment Research Committee of the Coordinating Research Council, Inc.) 710675

During the fall and winter of 1970-1971, the Coordinating Research Council (CRC) contracted with Southwest Research Institute for the latter to conduct a pilot program on 10 pairs of 1971 model cars to compare the influence of leaded and unleaded fuels on octane requirement increase (ORI). The cars were operated for 8,000-10,000 miles in the San Antonio area using a prescribed city-suburban driving schedule. One car of each pair was run on a commercially available leaded gasoline of 93 Research octane number (ON) and the other on a specially prepared unleaded fuel of similar quality. Differences in ORI for the two fuels ranged from 0-3.5 ON within car pairs. The average ORI of 4.0 ON for leaded fuel cars and 4.6 ON for unleaded fuel cars was not significantly different above the 80% confidence level.