The object of the present invention is to provide a process for experimental determination of heavy live crude oil dynamic viscosities reliable at a constant temperature (from ambient temperature to 463 K) and pressures from 68.9 MPa to the atmospheric pressure, including the dynamic viscosity at the bubble point pressure and by below of this point, based on a simple, reliable and accurate apparatus. The apparatus used in the present invention is based on an electromagnetic concept, only using a mobile element (piston) through a fluid at a constant force. The time required for the piston to travel a fixed distance is related exactly to the dynamic viscosity of the fluid contained in a measuring chamber. When the fluid contained in the inner part of the measuring chamber is more viscous, the piston displacement will be slower.