The global and partial solubility parameters and radii of interaction spheres of two copolymers recommended as viscosity improvers for multi-grade mineral oils - INFINEUM SV 260 and KELTAN 4200 - were determined from solubility data and intrinsic viscosities using 13 solvents both by the classical Hansen's method and an improved one. The obtained results are in good agreement each other and with intrinsic viscosity data. The values of the intrinsic viscosities obtained using the mineral oil SAE 10W as solvent, for which the two copolymers are intended to be used as viscosity improvers, show that it can be considered practically a very good solvent for INFINEUM SV 260 and a good one for KELTAN 4200.