"The new physical mechanism" of viscosity reduction of petroleum fluids Was Suggested in it series of recent publications. The key idea is that magnetic field treatment aggregates colloidal particles inside a Crude oil into larger ones, thus decreasing viscosity. On the basis of new experimental data and the analysis of well-proven theoretical models, we conclude that this "physical mechanism" in magnetically treated oils appears to be non-existent. In particular, as revealed by our optical measurements, magnetic treatment results ill disaggregation of colloidal particles in a crude oil.