Whats the difference between gl4 and gl5 gear oils?

Answer 1

GL-4 and GL-5 are standards set by the American Petroleum Institute for gear oils. GL-4 are intended for axles with spiral bevel and hypoid gears operating under moderate to severe conditions of speeds and loads. They are also suitable for sychronized manual transmissions when MT-1 gear oils are NOT recommended. GL-4 should be used in limited-slip differentials. The GL-4 generally indicates "Limited Slip" properties in the gear oil; sometimes abbreviated as LS. GL-5 is indicated for high-speed/shock loads and low-speed/high-torque conditions. GL-5 also has multi-purpose or mild EP (extreme) properties too. GL-5 is often seen with the MT-1 designation too. MT-1 indicates lubricants intended for NON-sychronized manual transmissions. MT-1 indicates the additional additives necessary to protect against thermal degradation, component wear and oil-seal deterioration which are not requirements by GL-4 or GL-5 approval. GL-5 is not the latest and greatest improvement over GL-4; unlike oil classifications where higher classification numbers mean tougher standards and backward compatiblity. It is important to know what type of gears you are lubricating, their applications and follow the manufacturer's recommendations! More information can be found at www.api.org.