Fluid solutions, e.g. mineral oil solutions, of polydispersed polymers have improved resistance to mechanical shear when said polymers have a narrow molecular weight distribution, i.e. ##EQU1## 10 and/or a reduced compliance less than that of a linear monodisperse polymer of the same chemical repeat unit and M.sub.w and preferably said solution at a concentration such that [.eta.] c ranges from one-tenth to five where [.eta.] is the intrinsic viscosity of the polymer in the oil and c is the concentration in the same units and/or has a compliance no larger than twenty times the value exhibited by an identical solution except that said polymer was replaced by a linear monodisperse polymer of the same chemical structure and of the same (.+-.5%) weight average molecular weight (M.sub.w).