The Royal Purple Max Gear Oil has been specially formulated to offer ultimate lubrication to differentials, manual transmissions, as well as lower gear units of marine engines that specify use of API GL-5, or GL-4 fluid. This lubricant is non-corrosive to soft yellow metals such as brass, bronze, copper, etc. It is synchronizer safe, and specially designed to extend both gear, and bearing life. Royal Purple engineered this lubricant to be ultra-tough gear oil to provide maximum protection to heavily-loaded gears while maximizing power throughout the drive train. The Max Gear will outperform ordinary gear oils by combining the highest quality synthetic oils with Royal purple’s proprietary Synerlec additive technology. Max Gear allows gears to run smoother, quieter, cooler, as well as longer without the need of overhauls. Trucks, as wheel as 4-wheel drive vehicles can benefit from this lubricant with the direct reduction of drag in the drive train. This particular Max Gear Oil is available in the 75W90 viscosity.