This disclosure relates methods and systems for determining asphaltene inhibitor properties. For example, one embodiment provides a method for determining a content of disaggregated asphaltene in an inhibited crude oil. The method includes measuring the dielectric constant of a sample of the crude oil, the sample having a first concentration of an asphaltene inhibitor; providing a first dielectric correction factor for the first concentration of the asphaltene inhibitor; calculating, e.g., by a computing device, a first corrected dielectric constant of the sample having the first concentration, using the first dielectric correction factor; and determining the content of disaggregated asphaltene in the first crude oil sample, based on the first corrected dielectric constant. Methods for inhibiting asphaltene aggregation in crude oil are also provided.