This study investigates the effects of liquid contamination factors, including water, cutting fluid, and anti-rust oil, on the tribological properties of two lithium-based greases. Results show that these factors increase the friction coefficients and wear behaviors of both Li_M and Li_S greases. Empirical equations establish a correlation between the concentrations of contaminants and the specific wear rate of greases, showing not only the quality of the greases, but also their capacity to withstand the effects of liquid contaminants. The presence of water or cutting fluid in the tested greases decreases the tribofilm thickness, which is attributed to the grease–water spray phenomenon on the steel ball surface outside the wear scar. Li_M grease, characterized by a high total acid number and water retention capacity, has less friction and higher wear resistance than Li_S grease, but in the presence of contaminants its behavior is similar, with a slight improvement in Li_S grease. Moreover, the addition of water to the greases significantly increases the level of vibrations. These findings provide fundamental information for the selection of greases to be used under wet performance conditions.