The stirring resistance caused by thickener is an important factor on the running torque of a ball bearing lubricated with grease.Therefore, grease development which aimed at running torque reduction by decrease of stirring torque has been carried out.However, it has been still unclear to reveal the effect of the molecular structure of thickener and the affinity between thickener and base oil on stirring torque. This paper reports the effects of transition point of viscoelasticity (Tve: defined as G’’/G’) on stirring torque, quantifying the difference between the running torque of the bearing lubricated with grease and base oil as stirring torque caused by thickener. The result indicated that stirring torque decreased as the increase of Tve. In addition, it was clarified that the affinity between thickener and base oil and surface area of the particle size of thickener, which were determined by molecular structure of thickener, highly affected on Tve. From these knowledges, in the case where the grease has low affinity and particle of thickener has large surface area, the grease would have high Tve and provides low torque.

Lubricating oils have been used to various mechanics, but the performance of the machine degrades when lubricating oils are deteriorated. In recent years, oxidation degradation of the turbine basis oil becomes a serious problem in the combined cycle power plant. This problem is caused by varnish that is produced oxidation products. Therefore, it is important to detect a sign of oxidation degradation from early stage of degradation. Authors have developed new deterioration diagnosis method for lubricating oils by the colorimetric analysis of membrane patches. In the previous study, we investigated the relation between oxidation process of the turbine oils with additives and change of color of membrane patches. But, it is important to understand the hydrocarbon oxidation process because lubricating oils is mainly composed of hydrocarbon. In this study, the influence of oxidation process of hydrocarbon on the color of membrane patches was investigated. And we investigated the influence of hydroperoxide on the color of membrane patches. As a result, the color of membrane patches became to brown color as oxidation of hydrocarbon. And color parameters of the membrane patch increased with increasing hydroperoxide number.