  We present a detailed AC susceptibility investigation of the fluctuation
regime in the insulating cubic helimagnet Cu2OSeO3. For magnetic fields mu_0 H
>= 200 mT, and over a wide temperature range, the system behaves according to
the scaling relations characteristic of the classical 3D Heisenberg model. For
lower magnetic fields the scaling is preserved only at higher T, and becomes
renormalized in a narrow T range above the transition temperature. Contrary to
the well-studied case of MnSi, where the renormalization has been interpreted
within the Brazovskii theory, our analysis of the renormalization at H = 0
shows the fluctuation regime in Cu2OSeO3 to lie closer to that expected within
the Wilson-Fischer scenario.
