Patent ID: 8854058

Claim:
A method of measuring a degree of degradation/alteration of a lubricating oil, the method comprising: measuring a dielectric constant or electrostatic capacitance of a lubricating oil at two or more different frequencies; and determining a degradation/alteration state of the lubricating oil based on values of the dielectric constants or the electrostatic capacitances, measuring a dielectric constant (∈ 1 ) or an electrostatic capacitance (C 1 ) of the lubricating oil at H 1 and a dielectric constant (∈ 2 ,) or an electrostatic capacitance (C 2 ) of the lubricating oil at H 2 ; and determining that the lubricating oil has been degraded/altered when a value of the dielectric constant (∈ 1 ) or the electrostatic capacitance (C 1 ) or the dielectric constant (∈ 2 ) or the electrostatic capacitance (C 2 ) has reached a set value; and predicting a degradation/alteration mechanism of the lubricating oil based on a rate of a change in dielectric constant with respect to the frequency [(∈ 1 -∈ 2 )/(H 2 -H 1 )] or a rate of change in electrostatic capacitance with respect to the frequency [(C 1 -C 2 )/(H 2 -H 1 )], wherein one frequency (H 1 ) of the two or more different frequencies is in a range of 5 to 80 Hz, and another frequency (H 2 ) is more than H 1 and in a range of 1,000 Hz or less.