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API Classes Gear Oils

API GL-1

Oils for light applications. The oils don’t have any additives. There may sometimes be small amounts of antioxidants, anti-corrosive elements or foam-inhibitors. The API GL-1 classification is for bevel gear tooth systems, worm drives and unsynchronised control gears in trucks or agricultural machines.

API GL-2

Oils for moderate applications. The oils contain wear-retardant additives and are designed for heavily stressed control gears. Recommended in tractors and agricultural machines for the proper lubrication of gears.

API GL-3

Oils for moderate applications. The oils contain up to 2.7% additives. For lubricating bevel gears and truck gears. Not recommended for hypoid gears.

API GL-4

Oils for light to heavy usage. The oils contain up to 4% effective, wear-retardant additives. For lubricating bevel gears and hypoid gears with little offset, truck gears, and rear axle gear units. Recommended for unsynchronised gearboxes in US American trucks, tractors and omnibuses and for the main and auxiliary gears of all vehicles. These oils are the minimum standard in Europe for all synchronised gearboxes.

API GL-5

Oils for harsh conditions. The oils contain up to 6.5% effective, wear-retardant additives. For lubrication of bevel gears and hypoid gears with large offset. A universal oil for all differential gears except gear-shifting gears. Some of these oils display special manufacturer’s releases, which can then only be used for lubricating the corresponding gear-shifting gears. Oils according to API GL-5 can be used in limited slip differentials if the oils correspond to the specifications according to MIL-L-2105D or ZF TE-ML-05. Typically, the classification is, for instance, API GL-5+ or API GL-5 LS.

API GL-6

Oils for very harsh conditions (very high sliding speed in the tooth flanks and considerable impact loads). The oils contain up to 10% of effective, wear-retardant additives. The specification GL-6 was removed because it became evident that GL-5 meets the specifications adequately.