Ionic liquids have increased the possibilities of Enhanced Oil Recovery (EOR) with surfactants. However, results obtained with only one of these salts as surfactant are not particularly promising. Best results are obtained with blends of these salts or blends with traditional surfactants. This work aims to break new ground regarding the role of ionic liquids in this application. Many traditional surfactants in EOR fail because they are not sufficiently soluble at optimal salinity in water. The possibilities of design of ionic liquids must also be considered to use them as co-surfactants in optimal formulations for oil recovery. In this work, the phase behaviour of the ionic liquid 1-hexyl-3-methylimidazolium acetate with water and different model oils (n-octane, cyclohexane and toluene) was determined at 298.15 K and 323.15 K. The complete miscibility of the ionic liquid with water and its low miscibility with the different oils, point to the use of 1-hexyl-3-methylimidazolium acetate as co-surfactant with surfactants with high oil solubilising capacity. (C) 2018 Elsevier B.V. All rights reserved.