Abstract: An oil monitoring system storing a remaining percent tachometer oil life, a remaining percent time oil life and a remaining percent odometer oil life. The oil monitoring system has means for selecting and displaying the lowest of these three remaining percent oil life values as the lowest remaining percent oil life. The selected lowest remaining percent oil life is compared to predetermined percentages to display on an in-vehicle display if the oil is OK, if the oil is to be changed soon, or if an oil change is required. The oil monitoring system may include an oil dielectric constant sensor and display if the oil is to be changed soon or an oil change is required as a function in the change in the oil's dielectric constant.

Abstract: Engine lubricating oil temperature and the amount of engine usage are used to calculate when engine lubricating oil has reached the end of its predicted wear life. Each spark (engine speed) pulse is multiplied by weighting factors that are periodically determined by sampling the engine oil temperature and the length of time the engine has been in continuous use above a predetermined speed. When the value of the accumulated weighted spark pulses has reached a predetermined level, a warning signal is provided to indicate the necessity of changing the engine lubricating oil.