The Sub-Committee of Octane Number Requirements (ONR) of the Japan Petroleum Institute has made a 1982 ONR survey on 120 Japanese passenger cars, including 39 cars with automatic transmission of 15 different models.Since the 1975 ONR survey, the minimum mileage required to keep stable ONR has been increased to over 6, 000km.Test vehicles and engine types are shown in Table 1.Primary Reference Fuel (PRF) and two types of unleaded Full Boiling Range Reference Fuel (FBRRF), cracked type and mixed type, have also been used as reference fuels.The blending proportions for preparing the FBRRF and properties of the blending stocks are shown in Tables 2 and 3, respectively.The low speed test method was mainly carried out on ten chassis dynamometers belonging to the participant companies and partly at the test track of the Japan Automobile Research Institute.The simulated road load on the chassis dynamometers was set arbitrarily by each participant but the inertia weight on the chassis dynamometer was set equal to the total vehicle weight.The determination of knocking was performed according to the JPI Standard Method 6R-6-77.The low speed knocking was identified in engine speed range from 1, 000rpm to 4, 000rpm during acceleration at the highest gear position.The test results obtained were treated statistically according to the JPI Standard 6R-2-72 in order to calculate the car satisfaction distribution for each of the given octane number fuels.For these statistical data, ONRs of 94 cars surveyed in 1981 were incorporated in the calculations, since the 1982 model cars contain the ones similar to those of the 1981 model cars which have been already tested.These results are shown in Table 8 and illustrated in Fig. 1.The low speed ONRs of 1982 model cars for 50% and 90% market satisfaction with the PRF were 90.8 and 95.7 octane numbers, respectively.The ONR distributions of 1982 model cars are summarized in Tables 5 and 6.