A new method to measure the magnetization dependence of the viscosity in polarized liquid He3 is presented. The magnetization is obtained by "brute-force polarization" at 45 mK in magnetic fields up to 11 T; it is subsequently destroyed by saturation of the NMR signal. Our result, a relative increase of the viscosity of (31.5)×10-3 at 3.9% polarization and a pressure of 30 bars, disagrees with a prediction based on the "nearly metamagnetic" model.