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 comprised 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 polymer B has the formula: ##STR1## wherein R.sub.1 is H or an alkyl group having about 1 to about 8 carbon atoms, R.sub.2 is an alkyl group having about 1 to about 18 carbon atoms, x is about 50.0 to 99.8 weight percent and x is about 0.2 to about 50.0 weight percent.