When selecting liquid grease, you must prioritize NLGI Grade (typically 000, 00, or 0), which defines the consistency for centralized lubrication systems. Key performance indicators include Base Oil Viscosity (cSt at 40°C) for load-carrying capacity, Dropping Point to ensure stability under high temperatures, and Four-Ball Weld Load to verify extreme pressure (EP) performance. For high-speed machinery, ensure the grease has excellent mechanical stability and oxidation resistance to prevent sludge formation.