The current work aimed to perform a consistency test based on the Gibbs-Duhem equation in order to evaluate experimental results obtained by supercritical carbon dioxide extraction of crude oil modified with several co-solvents in pressures of 20-60 MPa at 60 degrees C. The collected oil represented a liquid phase fraction while the outgassing losses a vapour phase fraction obtained after extraction. The systems of crude oil and ethanol or methanol modified supercritical carbon dioxide exhibited negative deviations from the Lewis-Randall rule. The unique combinations of saturation vapour pressures that satisfied the consistency tests were determined for the systems with the co-solvents using the criterion of the even distribution of the data about zero line in the plots of area test. The obtained values can be used to determine the thermodynamic conditions where the maximum recoveries can occur and the regions where the multiphases exist. The current study demonstrates that the consistency test is able to evaluate supercritical carbon dioxide extraction data obtained at high pressures, when using a combination mode. (C) 2013 Elsevier B.V. All rights reserved.