A method (M1) for increasing the efficiency of surfactants in micro-emulsions by adding a polymeric additive (I) with hydrophobic unit(s) (A) and water-soluble unit(s) (B), in which the ratio of number-average mol. wts. (Mn) for (B):(A) is 2-1000, each unit (A) has an Mn of not more than 1000, and the polymer (I) consists of water-soluble unit(s) (B) with hydrophobic unit(s) at the chain end(s) and/or non-terminal hydrophobic substituents and/or hydrophobic unit(s) between the water-soluble units (B). Independent claims are included for (1) a method (M2) for suppressing lamellar phases in micro-emulsions by adding (I) (2) a method (M3) for expanding the temperature window of micro-emulsions by adding (I) (3) micro-emulsions (ME1) containing water, oil, surfactant and (I), in which the mol. wt. of the water-soluble component of (I) is greater than the mol. wt. of the hydrophilic component of the surfactant (4) bi-continuous micro-emulsions (ME2) containing water, oil, surfactant and (I) (5) micro-emulsions as above (ME3) in which the mass ratio of (I) to (surfactant + (I)) is not more than 0.2 and the mass ratio of (surfactant + (I)) to oil is not more than 0.5 (6) micro-emulsions as above (ME4) in which the mass ratio of (I) to (surfactant + (I)) is not more than 0.2 and the additive (I) has one or more hydrophobic units at one site in the molecule .
