Gear Oil
Gear oil is designed to protect vital components, including the gears and bearings in the drive axles and differentials, transmissions, industrial gear boxes and power take-off units. Gear oil generally has a higher viscosity for easier distribution and protection through the entire gear set.
GL-1 Gear Oil
These oils are designed primarily for low-use manual transmissions. They usually operate under such low pressure conditions that there are only minimal additives needed. Friction modifiers and extreme pressure additives disqualify an oil from performing in this category.
GL-2 Gear Oil
These gear oils are used for worm-gear type axles, and can have additional additives on top of what is allowed in GL-1 oils. They’re still not allowed to use extreme pressure additives.
GL-3 Gear Oil
These oils are used for manual transmissions where the qualities of a GL-1 or GL-2 oil won’t suffice, but aren’t quite requiring the amount of load that a GL-4 oil can handle. They’re usually used for manual transmissions which are operating under moderate to severe conditions. They have a light extreme pressure effect.
GL-4 Gear Oil
These oils possess a moderate level of extreme pressure additives and are the most commonly used gear oil in the modern world. The majority of transmissions use this kind of oil.
GL-5 Gear Oil
These oils possess a very high level of extreme pressure additives. They’re primarily used with hypoid gears and other extremely loaded systems.
