SAE - Society of Automotive Engineers
It is the oldest classification for automotive lubricants, defining viscosity ranges and not taking into account performance requirements. It presents a classification for engine oils and another specific one for transmission oils. More information in "What do the numbers (20W-40, 50, etc.) that appear on oil packaging mean?".
API – American Petroleum Institute
Group that created, together with the ASTM (American Society for Testing and Materials), specifications that define performance levels that lubricating oils must meet. These specifications act as a guide for the consumer to choose. For passenger cars, for example, we have the API levels SL, SJ, SH, SG, SL, SM, SN, etc. Today we are already in an SN Plus or SN/RC. The “S” in this acronym stands for Service Station, or even SPARK (Spark) due to the use of Spark Plugs, explosion engines, and the other letter defines the level of performance. The first level was API AS, long obsolete, consisting of a pure mineral oil without any additives. With the evolution of engines, oils have undergone modifications, through the addition of additives, to meet the requirements of engine manufacturers with regard to protection against wear and corrosion, reduction of emissions and deposit formation, etc. Currently, the SN/RC level is the most advanced where the RC means “Resource Conserving” – Conservation of Energy Resources, such as emissions, Preservation of Turbo Systems and even specific for engines powered by Ethanol with up to E-85. In the case of diesel engines, the classification is API CI-4, CH-4, CG-4, CF, etc. The "C" stands for Commercial (Commercial Vehicles used to offer Services - always diesel engines) or "Compression", a specific operating process for diesel engines where there are no spark plugs and the explosion occurs by compression. The API also classifies oils for two-stroke engines and oils for transmission and gears.
ACEA - Association des Constructeurs Européens de l'Automobile (formerly CCMC)
European classification combines some API classification tests, European engine tests (Volkswagen, Peugeot, Mercedes Benz, etc.) and laboratory tests.
JASO – Japanese Automobile Standards Organization
Defines specification for the classification of lubricants for two-stroke engines (FA, FB and FC, in ascending order of performance).
NMMA- National Marine Manufacturers Association
Replaces the former BIA (Boating Industry Association), classifying lubricating oils that meet its requirements with the acronym TC-W (Two Cycle Water), applicable only to two-stroke outboard motors. Currently we find TC-W3 level oils, as the previous levels are in disuse.