To enable even an inexperienced person to quickly and accurately judge the specifications of a lubricant, the exchange timing to a new base, the replenishment timing of a new base and additive, or the like, by measuring infrared spectrum of an unknown lubricant, and estimating the shape, performance, or the like of an unknown lubricant from the model parameter of a calibration curve.

An infrared spectrum of a plurality of known lubricants including a base and a various kinds of additives is measured, the infrared spectrum is subjected to multivariate analysis for predicting description, performance, and the like. At the same time, the description, performance, or the like of a plurality of known lubricants are actually measured, and the model parameter of the calibration curve of an RBOT value consisting of a prediction value and an actual measurement value based on a plurality of known lubricant data is created. After that, the infrared spectrum is measured for the unknown lubricant for predicting the RBOT value, and the actual RBOT value is estimated from the prediction value and a previously created calibration curve. Then, a lubricant is controlled based on the estimated RBOT value.