Abstract: In the present work, quality of twelve commercial gear oil brands has been assessed by evaluating the physical characteristics and phosphorus contents. Physical parameters (Flash point, Pour Point, Viscosity index and Kinematic viscosity) and phosphorus contents were determined by standard test methods recommended by the American Society for Testing and Material (ASTM). Evaluated parameters have been compared with PSI standard specifications and the manufacturers specifications. Results indicate that none of the gear oil samples satisfy fully PSI standard test limits specified for Extreme Pressure Grade gear oils. Only a few samples have fulfilled the specifications given by the manufacturers. Marketing of sub-standard gear oil products in Pakistan is an alarming situation. Government of Pakistan should take strict measures to improve the quality of gear oils widely used in sophisticated machines.