Determining quality of lubricating oils in use

摘要

Resistivity rho values of a lubricating oil are repeatedly determined at a predetermined temperature (range) as it is in use in a working mechanism such as a vehicle engine. Such accumulated properties over operating time of the working lubricant can be plotted graphically to display a curve with, for example, a first portion where drho/dt>0, a maximum rho_max at a time t₁ where drho/dt=0, a second portion where drho/dt<0, a minimum rho_min at a time t₂ where drho/dt again is zero, and a third portion where drho/dt>0. Furthermore, there can exist another time t₃, where drho/dt exhibits a discontinuous change (increase) with time. Characteristics of the rho vs. t curve, including, the values of t₁, t₂, t₃, rho_max, rho_min, and the ratio rho_max/rho_min can be compared with like data on like lubricant oils in estimating the remaining useful life of the present operating lubricant oil.