SPECIFICATIONS FOR ENGINE OILS
All engine oils have the same function in principle. They are used to lubricate moving parts of the engine compartment and prevent corrosion and heat dissipation. Each engine is unique and therefore requires special oil properties in order to ensure optimal lubrication. These properties include a specific oil viscosity, temperature behavior, compatibility with certain sealants, and special flow properties. The additives to the oil are crucial in this instance. Several institutions have created various classifications and specifications to ensure users have a clear understanding. Vehicle manufacturers have the option to approve certain oils for their engines. These oils are not compatible with transmission oils.
Viscosity is a measure of the internal friction in a fluid. It is one of the most important properties of the oil. It is a measure of how viscous or thin an oil is and how it reacts to temperature. The SAE (Society of Automotive Engineers) has developed a system to define reference temperatures, viscosity limits, and class assignments for engine oil. Monograde oils are those that have a 100 deg C kinematic viscosity, such as SAE 30. These monograde oils were used back in the days when oil was only changed in summer and winter. Monograde oils are still used in many classic cars. Modern passenger cars use multi-grade oils, such as SAE5W30. Multi-grade oils are versatile and can be used throughout the year. They have excellent flow properties both in summer and winter. The flow behavior of oil at low temperatures is determined by the number preceding the “W”. The lower the number, the less liquid the oil will remain at low temperatures. This allows engine oil to quickly lubricate every important part of the engine, even during winter and cold starts. At 100 degrees Celsius, the kinematic viscosity is determined by the number after “W”. The oil’s resistance to extreme loads is greater if the number is higher.
Specifications according to the ACEA
ACEA stands for Association des Constructeurs Europeens de l’Automobile (Association of European Engine Manufacturers). It develops specifications for engine oils that are based on strict European testing procedures. The ACEA specifications are the most common denominator for European vehicle manufacturers’ requirements for engine oils. These specifications can be subdivided into sequences B, C, and D. The trucks only have the exclusive use of sequence E. These specifications are further differentiated by adding numbers to them.
- Sequence A – Describes the requirements for gasoline engines for passenger cars.
- Sequence B – Describes the requirements for diesel engines on passenger cars, vans, and pick-up trucks.
- Sequence C – Vehicles with advanced exhaust after treatment systems, such as diesel particulate filters, require special engine oils in order to prevent the engine oil from clogging. The permissible amount of ash-forming substances, sulfated ash, and phosphorus, as well as sulfur, determine which oils are suitable. These oils can be divided into low and mid-SAPS oils and then classified according to the ACEA C specifications.
- Sequence E – Describes requirements for diesel engines in trucks.
The engine oils for passenger cars must be a mixture of petrol and diesel engines (e.g., ACEA A3/B4. The letter number is followed by a number that describes the performance difference between the engine oils. We have summarized all ACEA specifications that are still valid in the table below.
Viscosity of HTHS
Oils with lower high-temperature viscosity are required for modern engines. This property is summarized by the term High-Temperature-High-Shear-Viscosity (HTHS). These oils reduce the viscosity at high temperatures, which decreases friction loss in the engine. This fuel can be used more efficiently, which results in lower fuel consumption and higher engine output.
Specifications according to API
API stands for American Petroleum Institute. API classes are American standards and quality criteria for engine oil. API S, API C, and API F are the three categories of specification for engine oils.
The letter “S”, which stands for passenger car petrol engines, is the code letter “C” (Commercial). The code letter “C”, which stands for Commercial, defines the requirements for diesel engines used in trucks and commercial vehicles. The API F standard was also introduced at the end of 2016 for commercial vehicles. For oils with an HTHS value greater than 3.5 mPas, the API CK-4 specification was created for backward compatibility. Modern engines can use oils with API FA-4 release. The HTHS value ranges between 2.9 to 3.2 mPas. Further emission reduction is the main focus.
API is not used to classify passenger car diesel engines. To keep the standards up-to-date, letters S and C are continually added along with additional numbers or letters. API SP and API CK-4 currently represent the most current specifications. They are compatible with older standards.
Specifications according to JASO
JASO (Japanese Automotive Standards Organization) is a Japanese organization that sets its oil specifications. The organization focuses on oil for two-stroke engines, as well as four stroke petrol engines and motorcycle engines. Special requirements are listed for motorcycle oils that are used in integrated transmissions (oil-bath clutches). Class JASO MA is for oils that are recommended for oil bath clutches, and class JASO MMB is for oils that are not recommended.
Specifications according to ILSAC
ILSAC stands for International Lubricants Standardization and Approval Committee. Representatives of American and Japanese vehicle manufacturer’s associations founded the organization. It issues oil specifications for Asian and American vehicles. The API is the basis of the oil standards, with a focus on petrol engines. Current standards are ILSAC GF-5 and ILSAC GF-6. These standards can be divided into 6A or 6B.
Additional requirements may be issued by certain automobile manufacturers to meet international specifications and classifications. These are named after manufacturer-specific standards (e.g., BMW Longlife-04, MB release, Porsche A40, etc.