Robust On-Board Engine Oil Monitoring. 2. Determination of Initial Oil Quality and Oil Aeration from Electrical Resistivity and Permittivity

Electrical ac impedance measurements were used for tracking the time dependence of the electrical properties (resistivity and permittivity) for 18 fully formulated engine oils during two types of engine dynamometer tests: high-temperature high-load (HTHL) and postal cycle (PC). The signatures in the time dependence of the electrical resistivity of engine oil at beginning-of life (BOL) and during early service differentiate both oil service classifications and test/driving conditions. The air content in engine oils can be determined quantitatively from the permittivity with a detection limit of 0.2 vol%. The significance of our results and their consequences for on-board monitoring of engine oil through sensing technology based on electrical ac impedance measurements are discussed.