A method for controlling the viscosity of organic liquids, said organic liquid having a solubility parameter of from about 6 to about 10.5, which comprises incorporating in said organic liquid a minor amount of a polymer complex, said complex being formed from the interaction of polymer A, containing neutralized sulfonate groups and polymer B, containing basic nitrogen groups, both functional groups being presented at a level of from about 4 to 500 meq. per 100 g. of polymer, wherein the polymeric backbone of polymer A and polymer B are the same.