Full definition
Fundamental property for hydraulic system operation. Too low (<10 cSt): internal leakage, metal-to-metal wear. Too high (>100 cSt): suction cavitation, overheating, efficiency losses. Optimal operating range: 16-100 cSt (ISO VG 32-68). Viscosity index (VI): 95-110 standard, >140 multigrade (HVLP). Measured per ASTM D445. Viscosity drops ~50% for every 25°C temperature increase.