average changes quickly next at step 140 a change interval is calculated based on oil operating temperature equation 9 is applicable where the temperature measurement is in degrees fahrenheit or rankline for temperature measurements in kelvins or degrees celsius substitute 10 for 18 in the equation referring now to fig6 steps 72 to 88 of fig3 which relates analysis of oil dielectric constants on a vehicle equipped with the appropriate sensor are expanded upon beginning at step 150 the voltage across the dielectric sensor is measured and equated to the dielectric coefficient next at step 152 the temperature of the oil is taken the dielectric u201c constant u201d or coefficient of the oil is a function of oil temperature the oil 39 s dielectric coefficient also tends to increase slowly over time using the measured temperature a look up table 153 may be referred to in order to obtain a predicted value for the dielectric coefficient at the present measured temperature essentially the dielectric coefficient should be close to recently obtained values averages for which provide the values in look up table 153 comparative curves for new oil and hypothetical recent values are illustrated exemplifying how the dielectric constant moves higher as the engine oil ages oil the dielectric coefficient for which changes upwardly suddenly has likely been contaminated a sudden downward shift in the constant usually indicates that fresh oil has been added to an engine or that an oil change has been made step 154 provides for determining if such a sudden change in the dielectric coefficient has occurred by checking to see if the coefficient is between upper and lower bounds set based on the recent values for the constant if the values remain within bonds the just obtained value is filtered into the values used.