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The study about the dynamic characteristics of a great number of mechanical parts has been promoted by the necessity of decreasing the vibrational effects in mechanical systems, as the reduction of superficial fatigue. In this way, the research around, even, a simple part like a hydrodynamic bearing is very important, especially in the automotive industry. In this case, the lubricant acts like a flexible liking element between the journal-bearing surfaces. The lubrication is essential for the engine, because it reduces the wear between the internal parts and prevents the metal contact. Due to the shear stresses present in the lubricant, the temperature rises and, consequently, it changes the lubricant properties. The viscosity is strongly dependent on the temperature and it is the parameter that characterizes the fluid flow and its dynamic behavior. Any temperature change induces a consequent modification in the lubricant behavior.

Due to the huge demand for more efficient engines, as consequence of reduced pollutant emission, not only has the automotive industry been trying to achieve deeper understanding of the physical mechanisms present in the engines, but also to improve its mathematical modeling. Concerning the journal bearings, this task has extreme relevance, when either downsizing or repowering approaches are aimed to be performed. Regarding the mathematical models, identification of a model which is able to guarantee both reliable results and non-prohibitive computational costs should be achieved. This work aims to present the comparison between hydrodynamic and elastohydrodynamic simulation, showing the particularities of each approach and its advantages and disadvantages.