LUBRICANT SERVICE CLASSIFICATIONS AND SPECIFICATIONS

API SERVICE CLASSIFICATIONS (ENGINE CRANKCASE OILS)

The American Petroleum Institute (API) Engine Service Classification was developed as a result of a co-operative effort in the USA

between the API, the American Society for Testing and Materials (ASTM) and the Society of Automotive Engineers (SAE). The tripartite

was developed to form a means of communication between the engine manufacturers and lubricants suppliers.

The system defines classes of service for both petrol and diesel engine applications as well as stipulating the accepted engine

laboratory tests.

The letter ‘S’ (Service Station Classification) is designated for spark ignition engines (petrol engines) in passenger cars and light

commercial vehicles. For compression ignition engines (diesel engines), the letter ‘C’ (Commercial Classifications) has been

designated. The following is a brief summary of the API classifications.

API Base Oil Definitions

Group I base stocks contain less than 90% saturates and/or greater than 0.03% sulphur and have viscosity index greater than or equal

to 80 and less than 120.

Group II base stocks contain greater than or equal to 90% saturates and less than or equal to 0.03% sulphur and have viscosity index

greater than or equal to 80 and less than 120.

Group III base stocks contain greater than or equal to 90% saturates and less than or equal to 0.03% sulphur and have viscosity index

greater than or equal to 120.

Group IV base stocks are polyalphaolefins (PAO).

Group V base stocks include all other base stocks not included in Group I, II, III or IV.

API Automotive Gear Lubricant Specifications

API SERVICE CLASSIFICATIONS

The most important internationally accepted system defining automotive gear oil performance characteristics is laid down by the

American petroleum institute (API).

API GL-1

Designates the type of service characteristics of automotive spiral-bevel and worm gear axles and some manually operated

transmissions operating under such mild conditions of low unit pressures and sliding velocities that a non-additive mineral oil can be

used satisfactorily. Oxidation and rust inhibitors, anti-foam additives and pour point depressants may be utilized to improve the

characteristics of lubricant for this service. Does not contain friction modifiers and extreme-pressure agents.

API GL-2

Designates the type of service characteristics of automotive-type worm gear axles operating under such conditions of load,

temperature and sliding velocities that lubricants satisfying API GL-1 service will not suffice. Products suited for this type of service

contain anti-wear or very mild extreme-pressure agents that provide protection for worm gears.

API GL-3

Designates the type of service characteristics of manual transmissions and spiral-bevel axles operating under moderately sever

conditions of speed and load. These service conditions require a lubricant having load carrying capacity greater than that which will

satisfy API GL-1 service, but below the requirements of lubricants satisfying API GL-4 service. Lubricants designated for this service

typically contain additives that are active at the tooth surface at the temperatures resulting from high-speed or load.

API GL-4

Designates the type of service characteristics of gears in manual transmissions operating under sever conditions of sliding speed,

particularly spiral bevel and hypoid gears in moderate service, in passenger cars and other automotive-type equipment operated under

high speed/low torque and low speed/high torque conditions.

API GL-5

Designates the type of service characteristics of gears particularly hypoid, in passenger cars and other automotive equipment operated

under high-speed/shock load, high-speed/low-torque, and low-speed/high-torque conditions. Equivalent to MIL-L-2105D, this category

is mainly applicable to axles but may also be used for certain manual transmissions.

API GL-6 (Obsolete)

They type of service designated by API GL-6 is characteristic of gears, specifically high offset hypoid gears in passenger cars and

other automotive equipment operated under high-speed high-performance conditions. This classification is obsolete. The equipment

required for the test procedure to verify lubricant performance is no longer available.

API MT-1

This category defines a gear lubricant for heavy-duty manual transmissions that has thermal stability, high temperature cyclic durability

and copper compatibility level exceeding API GL-1 through GL-5. Gear lubricants in this category typically meet the service

requirements of non-synchronized manual transmissions in heavy-duty trucks and in buses.API Engine Service Categories (Gasoline/Petrol Engines)