The principle of the Full Automatic Octane Number of Engine Fuel Tester is to measure the octane number of gasoline, the insulation permeability and the electromagnetic induction charge characteristics. By measuring the dielectric properties of the oil and comparing it with the known data model stored in the memory, the result can be determined. The induction device is very, can measure the small dielectric parameter change. So it can detect the octane number petroleum product parameters.