A physical model for the engine oil condition sensor

The engine oil condition sensor has the capability of detecting three oil degradation stages: good, rapid increase of acidic decomposition products, and rapid increase of viscosity. In this work, a model was developed to correlate the sensor output with key engine oil parameters. Based on this model, the sensor output measured from a degraded engine oil should be linearly proportional to the concentration of acidic decomposition products and inversely proportional to the viscosity. This model was verified using the sensor output measured either in-situ from dynamometer engine tests or in the oil samples collected from the dynamometer rest. This model correlated the sensor output with key engine oil parameters except for engine oil with extremely high viscosity.