This paper reports experimental activity coefficients at infinite dilution, gamma(not similar to)(i), for methanol, ethanol and n-hexane in three refined vegetable oils (soybean, sunflower, and rapeseed oils) measured using the dilutor technique (inert gas stripping method). The measurements were carried out in the temperature range between 313.15 and 353.15 K. Furthermore, activity coefficients at infinite dilution for various solutes (acetone, methanol, ethanol, n-hexane, cyclohexane and toluene) were measured in capric (decanoic) acid using the same technique in the temperature range from 313.13 to 353.30 K. The new data obtained for capric acid and soybean oil were compared with already published experimental data. Additionally, densities of the investigated vegetable oils were measured in the temperature range from 293.15 to 353.15K. Using the experimental gamma(not similar to)(i) values obtained over the temperature range, the partial molar excess Gibbs energy (Delta G(i)(E,not similar to)), enthalpy (Delta H-i(E,not similar to)) and entropy (Delta S-i(E,not similar to)) at infinite dilution were determined. The relative error for the gamma(not similar to)(i) measurements carried out using the dilutor technique is approximately +/- 2.5%. The measured gamma(not similar to)(i) data in the investigated refined vegetable oils were also compared with the results of the group contribution methods original UNIFAC and modified UNIFAC (Dortmund) and an extension of the latter method to triacylglycerols was proposed. (C) 2013 Elsevier B.V. All rights reserved.