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The entire article is worth reading but this is particularly interesting to me:
"For several years, automakers like General Motors, BMW, and Mercedes-Benz have installed computerized systems that alert drivers via an instrument panel light when it?s time to change oil. As an example, the General Motor Oil Life System (GMOLS) analyzes the engine temperature, rpms, vehicle speeds, and other driving conditions to calculate the rate of engine oil degradation. Then, software calculates when the oil needs to be changed."
I wonder how accurate this could be?