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Intake valve deposits (IVD) and combustion chamber deposits (CCD) in spark-ignition engines greatly affect nitrogen oxides (NOx) emission and octane requirement increases (ORI) as they prevent the heat release from the combustion chamber and increase the compression ratio. Currently, fuel performance additives to control IVD and CCD have been attracted and evaluation method based on CCD weight and thickness has been widely used. However, simple measurement of the CCD weight and thickness does not clearly reflect the CCD effect on the ORI, as the shape and location of the deposits are also crucial factors that must be considered along with the weight and thickness of the deposits. In this paper, an ORI engine test procedure using a 4 cylinder 2.0 liter SOHC engine is introduced.