Red Line Oils Synthetic 80W140 Gear Lube, Quart Red Line's 80W140 Synthetic Gear Oil is generally used in commercial trucks which will climb long, steep grades and some racing applications where power is not critical. Generally 0.5% less efficient than 75W90. It can also be used in differentials and transmissions where excessive noise is a problem and limited-slip differentials which vibrate excessively when turning a corner and exceeds API GL-5. Red Line's Synthetic Gear Oil's are designed to provide the highest degree of protection and greatest efficiency for your drivetrain. Red Line provides a complete line of drivetrain lubricants which are optimized for differential, transmission, or transaxle use over a wide range of temperatures. Proper selection depends upon the manufacturers' requirements and whether the application is for passenger automotive, commercial, or racing use.