The measurement model technique was used to analyze impedance data associated with Cronidur 30 and M50 steel samples in new and degradedjet engine oil. The analysis for the degraded oil included both determining the error structure associated with the data and evaluating the consistency of the data with Krarners-Kronig relations. Voiat measurement model parameters were used to identify characteristic time constants for new and degraded oils. This information was used to differentiate the impedance responses into bulk oil and alloy-oil interfacial contributions. The analysis presented here represents a step toward understanding the physical processes involved. (c) 2005 Published by Elsevier Ltd.