While industrial gear lubricants are often marketed under trade names, information is always available as to how these products conform to AGMA numbers . Therefore, little difficulty occurs with the designation of this time of gear oils.
However, in the case of automotive transmission and axle types of oils the marketing designation has not always been clear and is, in fact, sometimes misleading. The SAE Handbook, in about 1924, started to include SAE viscosity numbers for such lubricants, and when , in 1951, API approved definitions for ‘Regular-Type Gear Lubricant,’’ ‘Mild Type EP Gear Lubricant,’’ and ‘Multipurpose Type Gear Lubricant’’ these terms were suggested for use by SAE. With the availability of improved EP gear oils, as mentioned above, the API Lubricating Committee, in 1957,agreed that such products should be known as ‘Multipurpose Type Gear Lubricants (API Service GL 4).” Such oils were described as follows:
“This term designates Lubricants which have adequate load carrying ability and other required properties to protect hypoid gears in sustained high speed and /or high torque service in modern high powered passenger cars and trucks. Also suitable for use in spiral bevel gears, many transmissions, and worm gears in some types of service. Such Lubricants are identified as meeting ‘A.P.I. Service GL4’.’’
The consumer of gear lubricants should bear in mind that such products are like other commodities, in that , while a conscious organization may set tolerances for material to be supplied under a given designation, some products offered will barely meet the required specifications. Therefore, the purchaser or user of gear oils should deal only with reputable firms.
