Gear Lubricants
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Background & Properties
Industry Specifications
July 2017
API Gear Oil Classifications
Service Designations in Current Use:
Classification Description Uses
API GL-1 Straight Mineral Oil Manual transmissions operating under
mild conditions.
API GL-4 Equivalent to Manual transmissions, axles with spiral
MIL-L-2105 bevel gears operating under moderate to
severe conditions of speed or load, hypoid
gears operating under moderate to
severe speeds and loads and transaxle
applications where API MT-1 lubricants
are unsuitable.
API GL-5 Virtually equivalent Gears, particularly hypoid gears, in axles
to MIL-L-2105E operating under various combinations of
high-speed shock loads and low speed,
high-torque conditions.
API MT-1 Thermally stable Nonsynchronized manual transmissions used
and contains EP in buses and heavy-duty trucks.
additives
Service Designations Not in Current Use:
Classification Description Uses
API GL-2 Usually contain Automotive worm gear axles.
fatty materials
API GL-3 Mild EP additives Manual transmissions operating under moderate
to severe conditions and spiral-bevel axles
operating under mild to moderate conditions of
speed and load.
API GL-6 Obsolete Gears with very high pinion offsets.
Reprinted from Lubrizol's Ready Reference for Lubricant and Fuel Performance.
Due to obsolescence or inability to verify test requirements from unavailable equipment, this manual will not discuss
API GL-1 through API GL-4 and API GL-6.
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