The symmetric CH3-stretching mode nu(1) of CH3I is investigated in a solution of CDCl3 in the concentration range 7-100% and temperature interval 242-374 K using time-resolved coherent anti-Stokes Raman scattering (CARS) with 250 fs pulses and magic polarization geometries. Striking deviations from simple exponential relaxation dynamics are reported for mixtures with mole fractions around 0.5. Analysis of the concentration dependence allows to distinguish the dephasing contribution of concentration fluctuations with correlation time >1 ps, indicating the intermediate case for this relaxation mechanism. The results are well described by the Knapp-Fischer model for concentration fluctuations, yielding a molecular residence time in the solvation layer of 1.1-3.2 ps in the temperature range 242-374 K in accordance with theoretical estimates.