Method for managing lubricant oil, and method for predicting life of lubricant oil

A lifetime expectancy prediction method of a measurement oil by determining a degradation degree of the measurement oil in a form of a used lubricating oil comprising an antioxidant, the method comprising:

• obtaining a determination value of the measurement oil according to a determination method a and a determination method b below;
• subjecting the measurement oil to a degradation process for a predetermined time until the lubricating oil reaches a threshold value representing a usage limit of the lubricating oil, and obtaining a determination value of the measurement oil after being subjected to the degradation process according to the determination method a and the determination method below;
• and
• predicting a lifetime expectancy of the measurement oil based on a time of the degradation process in the subjecting step, the determination value, which is obtained in the subjecting step, of the measurement oil after being subjected to the degradation process, and the determination value, which is obtained in the obtaining step, of the measurement oil,
• wherein:
• the determination method a comprises:
• measuring an infrared ray absorption spectrum of the lubricating oil with a Fourier transform infrared spectrometer, and
• calculating a total content of the antioxidant and an altered substance having the same functional group as the antioxidant to determine a deterioration degree of the lubricating oil from the obtained content;
• and
• the determination method b comprises:
• filtrating the lubricating oil with a filter,
• subsequently measuring a color difference of substances captured by the filter with a colorimeter, or measuring a color difference of the lubricating oil with the colorimeter, and
• determining a degradation degree of the lubricating oil and a mixture degree of foreign substances based on the color difference of the substances or the color difference of the lubricating oil.