The performance of an on-board oil quality sensor is evaluated and shown to reliably measure motor oil degradation in real-time over the temperature range found in a vehicle. This sensor operates by utilizing a conductive polymeric matrix to track the change in the solvent properties of an oil. Tracking oil degradation by a change in its solvent properties provides a means of directly measuring 1) oil oxidation and 2) water and antifreeze contamination. The sensor shows a relatively constant signal between fresh oils but offers a clear separation between degraded oils. Results are shown to compare favorably with complementary methodologies including infrared spectroscopy, differential scanning calorimetry, thermogravimetic analysis, dielectric analysis, and metal analysis.