Description:
3 min
Oil Classification
Modern engine oils are usually classified based on various parameters organized in several main standards:
SAE, Society of Automotive Engineers – the American Society of Automotive Engineers. The specification of this organization, SAE J300, is one of the most important as it categorizes oils by viscosity and is certainly the most well-known. It divides oils into subcategories theoretically based on seasonality, but in reality, the majority of motor oils are all-season oils. This is indicated by the letter W (Winter) between the oil's temperature coefficients.
The first digit before the letter represents the low-temperature coefficient. It indicates the lowest temperature at which the oil's fluidity is sufficient to start the engine. Naturally, the order is not direct but encoded: you subtract 40 from the numerical designation. For example, the oil with the designation 0W30 can be used at a temperature of -40°C.
The numbers after the alphabetical index represent the high-temperature coefficient. It determines the range of kinematic viscosity at 100°C and dynamic viscosity at 150°C. Manufacturers usually recommend grade 30 for new engines (e.g., 5W30), while grade 40 is recommended for engines that have run 25% or more of their lifespan.
API, American Petroleum Institute – the American Institute of Petroleum. This specification establishes working standards and quality levels for oils and, depending on their performance properties, prescribes their use in different types of engines. The marking S (Service) denotes suitability for gasoline engines, C (Commercial) for diesel engines, T (Two-stroke) for two-stroke engines, and a dual marking (e.g., SG/CD) indicates applicability to both types of engines.
The next letter in the marking signifies the intended use for engines produced within a specific time period. The further along the alphabet, the more modern the oil. Today, oils of specifications SN/SM and CJ-4/CI-4 are mainly used. Upgrading to a higher standard is permissible, but downgrading is not.
It is worth noting the API EC (Energy Conserving) category separately. These are energy-conserving oils with low viscosity that improve fuel efficiency by approximately 2-4%.
ACEA, Association des Constructeurs Européens d'Automobiles – the Association of European Automobile Manufacturers, sets requirements for engine oils from leading European automotive firms. According to separate tests, ACEA specifications significantly exceed API requirements. Therefore, ACEA classification is considered more informative and allows for a more precise selection of engine oil.
ACEA standards are divided into classes based on oil applications:
• A – for gasoline engines;
• B – for diesel engines up to 2.5 liters;
• C – for gasoline and diesel engines equipped with catalysts;
• E – for diesel engines over 2.5 liters.
In addition, each class implies a division based on working characteristics, indicated by numbers:
• 1 – energy-conserving oils;
• 2 – oils for general use;
• 3 – high-quality oils with extended drain intervals;
• 4 – oils for direct injection engines;
• 5 – oils with the highest operational properties and extended change intervals.
Excluding classes A1/B1, increasing numeration indicates an improvement in oil category. Although recommendations for the use of these oils may vary among different car manufacturers, it is generally advisable to prefer oil brands that have undergone ACEA testing. European standards have stricter requirements compared to American standards.
ILSAC, International Lubricant Standardization and Approval Committee – an international committee for the standardization and approval of engine oils jointly created by the American Automobile Manufacturers Association (AAMA) and the Japanese Automobile Manufacturers Association (JAMA). Similar to ACEA, ILSAC classification imposes stricter requirements on
motor oil manufacturers compared to API. However, ILSAC standards are often regarded as an additional subclassification of API specifications, although they are autonomous.
Compared to API, ILSAC additionally regulates:
• Oil functionality under high-pressure conditions (shear stability);
• Fuel economy;
• Oil volatility;
• Viscosity;
• Foaming;
• Filtration at low temperatures;
• Presence of phosphorus.
As of today, the most advanced categories introduced on 01.05.2020 are GF-6A, which corresponds to the API SP Resource Conserving category, and GF-6B, which applies only to SAE 0W-16 oils and is not backward compatible with previous API and ILSAC categories.
These are the main specifications that are most commonly encountered in car manufacturers' user manuals. In addition to the ones mentioned above, there are others as well. In our country, for example, there is the AAE (or AAI – Association of Automotive Engineers) oil classification, approvals from specific car manufacturers (Mercedes, VW, Renault, etc.) – quality and compatibility standards for oils with engines. However, all these specifications address operational and dynamic characteristics of oils. Meanwhile, there is another parameter that is also very important when selecting oil.