Several regimes of the (T, x1, x2) surface of the liquid–liquid phase diagram at or close to a nominal pressure of 0.1 MPa of the ternary systems 1-hydroxyethyl-3-methylimidazolium based ionic liquids (1), [C2OHmim][X] ([X] = [PF6]− or [BF4]− or [CF3SO3]− or [(CF3SO2)2N]−), +dichloromethane or 1,2-dichloroethane (2), +2-propanol (3) were investigated. For the first time, phase splitting in a (IL + dichloromethane) system was found and the related temperature–composition phase diagrams for all aforementioned ILs were determined. In the case of 2-propanol, partial miscibility was observed only for ILs containing the [PF6]− and [BF4]− anions. When the latter are involved in ternary systems, the ternary phase diagrams at ambient conditions show wide areas of total miscibility, thus revealing an unexpected and large co-solvent effect. For the ternary mixture ([C2OHmim][PF6] + dichloromethane + 2-propanol), a moderate pressure effect on the cloud point with a negative pressure–temperature slope was detected.