Abstract: Herein disclosed is an oil degradation warning system for an engine equipped with a turbocharger. The system comprises first means for detecting the temperature of the engine oil in the turbocharger, second means for deriving a correction coefficient from informations issued from the first means; third means for multiplying a predetermined time increment by the correction coefficient to derive a modified time increment; fourth means for integrating the modified time increment to derive a time dependent oil degradation value; and fifth means for issuing a warning when the time dependent oil degradation value becomes equal to or larger than a predetermined value.

Abstract: Disclosed herein is an oil degradation warning system of a motor vehicle, which can issue a warning at the time when the oil change is really needed. The system comprises first means for detecting respective values of degradation factors of oil, the degradation factors being closely related to the operation history of the motor vehicle, second means for adding the values by using a predetermined calculation formula and integrating the added result with passage of time, third means for issuing a warning signal when the integrated result exceeds a predetermined limit, and fourth means which, when oil replenishment is carried out, postpones the issue of the warning signal in accordance with the amount of the replenished oil.

Abstract: In order to obviate the need to manually input data relating to the grade of oil used to lubricate an engine, a monitoring system includes a sensor which senses the grade of oil along with sensors which enable the oil change procedure per se to be detected. After each oil change the output of the oil grade sensor is read and the appropriate values which determine the limits to which the oil may be permitted to degradate are automatically determined.