A vibratory flow meter (5) for determining a viscosity of a flow material is provided according to the invention. The vibratory flow meter (5) includes a meter assembly (200) configured to generate a density (p) of a flow material, generate a first mass flow rate (m1) for a first flowtube (210a), and a second mass flow rate (m2) for a second flowtube (210b). The vibratory flow meter (5) further includes a restrictive orifice (252) located in the first flowtube (210a). The restrictive orifice (252) ensures that a first flow rate of the flow material in the first flowtube (210a) is less than a second flow rate of the flow material in the second flowtube (210b).