I'll just leave this here. Some light reading for the interested.......
Fluid temperature stability is essential to the success of mechanical systems. All hydraulic and lubricating fluids have practical limits on the acceptable operating temperature range - both…
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"Fluid temperature grossly affects chemical stability and particularly the oxidation rate of the basic elements of the oil. The primary accelerator of all oxidation reactions is temperature. Like any other reaction, the oxidation rate of hydrocarbons will approximately double for every 18 degrees Fahrenheit increase in temperature.
Below 140°F, the reaction is comparatively slow, but engineers estimate that the life of an oil is reduced 50 percent for every 18 degrees Fahrenheit temperature rise above 140°F, according to the Arrhenius equation for chemical reaction rates. Hence, for high-temperature applications, the oxidation stability of an oil can have great significance and users should assess it carefully."