API system - Transmission oils
In its Publicaiton 1560 issued in January 1966, API stated a classification system for transmission oils with the following classification depending on the operating conditions of the oils. If any lubricant is suitable for more than one of the following classes, this will be stated.
The classification do not however include oils/fluids for automatic transmissions, torque converters, differential brakes, etc. These components require special lubricants.
API-GL-1
Relates to oils for motor vehicles with spiral bevel gears, worm gears and manual transmissions operated under conditions of low surface pressure and sliding velocities that a straight mineral oil can be used statisfactorily. Oxiation and rust inhibitors, foam depressants and pour point depressants are often used to improve the characteristics of these oils.
API-GL-2
Relates to oils for motor vehicles with worm gears operating under such conditions of load, temperature and sliding velocities that lubricants satisfactory for API-GL-1 will not suffice.
API-GL-3
Relates to oils for manual transmissions and rear axles with spiral bevel gears operating under moderately severe conditions of speed and load. These service conditions require a lubricant having load carrying capacities greater than those which will satisfy API-GL-1, but below the requirements of lubricants satisfying API-GL-4.
API-GL-4
Relates to oils for gears, particularly hypoid gears in vehicles operated under high speed/low torque and low speed/high torque conditions.
API-GL-5
Relates to oils for gears, particularly hypoid gears in vehicles operated under high speeds/low torque and low speeds/high torque conditions.
