Bearing performance characteristics such as stiffness, and load capacity, are related to the lubrication fluid circulating through the gap. In the fluid film bearings, the characteristic of the lubrication film also depends on the journal geometry and the viscosity. This study aimed to research the bearing geometry influences on the thermohydrodynamic performance of a circular journal bearing. The temperature distribution is modeled using a 3-dimensional en-ergy equation. The velocity components are obtained on the pressure distribution governed by Dowson’s equation. Moreover, the heat transfer between the journal and oil is modeled with Fourier heat conduction equation, and the viscosity equation is derived for SAE10W30 commercial oil as a function of the temperature. An algorithm based on the finite difference method is developed, and a serial simulation is performed for different geometrical parame-ters such as bearing clearance, and bearing length-to-diameter ratio (L/D). When the radial clearance decreases from 150 µm to 100 µm, the maximum pressure grows up by 53%, and the maximum temperature decreases by 21%. On the other hand, when the L/D ratio rises from 0.8 to 1, the maximum pressure grows up by 22%, but the temperature distribution does not significantly change. The load capacity, and the stiffness are higher for low radial clearance. The load capacity, and the stiffness increase when the L/D ratio grows up.