Abstract: Resistivity ? 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 d?/dt>0, a maximum ?max at a time t1 where d?/dt=0, a second portion where d?/dt<0, a minimum ?min at a time t2 where d?/dt again is zero, and a third portion where d?/dt>0. Furthermore, there can exist another time t3, where d?/dt exhibits a discontinuous change (increase) with time. Characteristics of the ? vs. t curve, including, the values of t1, t2, t3, ?max, ?min, and the ratio ?max/?min can be compared with like data on like lubricant oils in estimating the remaining useful life of the present operating lubricant oil.

Abstract: Method and apparatus for automatically replenishing additives lost from the lubricating oil of an IC engine, by injecting controlled quantities of the additive into the oil. The amount and frequency of injection is controlled by either the operating conditions of the oil (e.g. its thermal history), or changes the properties of the oil (e.g. its electrochemical activity, or dielectric constant).

Abstract: Method and apparatus for automatically replenishing additives lost from the lubricating oil of an IC engine, by injecting controlled quantities of the additive into the oil. The amount and frequency of injection is controlled by either the operating conditions of the oil (e.g. its thermal history), or changes the properties of the oil (e.g. its electrochemical activity, or dielectric constant).

Abstract: Leakage of engine coolant into the engine lubricating oil can be detected to high sensitivity levels by dissolving a glycol-soluble salt of 86Rb as a tracer in the coolant and detecting the beta or gamma ray radiation from the tracer containing coolant in a suspected leakage path or in the lubricating oil. A useful application of this detection method is in the region of the head gasket (i.e., between the cylinder block and cylinder head) of a liquid-cooled internal combustion engine.