A method includes disposing an open end of a housing in a wellbore fluid, flowing the wellbore fluid into the housing though the open end, rotating an impeller disposed within the housing at a first rotational speed with a motor coupled to the impeller, and determining at least one of viscosity and rheology of the wellbore fluid based on the rotating an impeller. An apparatus includes a housing, a mechanical agitator disposed in the housing, a motor operatively coupled to the mechanical agitator, a first sensor coupled to at least one of the mechanical agitator and the motor, and a second sensor disposed in the housing and configured to measure a fluid property or characteristic.