About EOLCS & API Symbol

Engine Oil Licensing and Certification System (EOLCS)

API's Engine Oil Licensing and Certification System (EOLCS) is a voluntary licensing and certification program that authorizes engine oil marketers who meet specified requirements to use the API Engine Oil Quality Marks—the API Service Symbol "Donut" and Certification Mark "Starburst".

This program is a cooperative effort between the oil industry and vehicle and engine manufacturers Ford, General Motors, and Chrysler; the Japan Automobile Manufacturers Association; and the Engine Manufacturers Association.

Performance requirements, test methods, and limits are cooperatively established by vehicle and engine manufacturers, technical societies like the Society of Automotive Engineers (SAE) and the American Society for Testing and Materials (ASTM) and industry associations like the American Chemistry Council and API.

Oils meeting these requirements are recommended by vehicle manufacturers.

THE API SERVICE SYMBOL

The API Service Symbol "Donut" is divided into three parts:

• The   top half   describes the oil's performance level.
• The   center   identifies the oil's viscosity.
• The   bottom half   tells whether the oil has demonstrated resourcing-conserving properties in a standard test in comparison to a reference oil.

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• Top - Performance Level  ​

The top of the Donut shows the oil's performance level for gasoline and/or diesel engines.

The letter "S" followed by another letter (e.g. SN or the latest, SP) refers to oil suitable for gasoline engines.

The letter "C" followed by another letter (e.g. CK-4) refers to oil suitable for diesel engines.

These letters officially stands for "Service" and "Commercial."

API has also announced the newest API FA-4 category for certain SAE xx-30 oils which is designed to protect the next generation of diesel engines.

The current API performance categories that can appear in the top part of the Donut are listed in the API Motor Oil Guide or you can refer to our API Classifications page.

• Center - SAE Viscosity Grade

The center of the Donut shows the oil's SAE viscosity grade.

Viscosity is a measure of an oil's flow characteristics, or thickness, at certain temperatures.

The low-temperature viscosity (the first number, 5W in a 5W-30 oil) indicates how quickly an engine will crank in winter and how well the oil will flow to lubricate critical engine parts at low temperatures. The lower the number, the more easily the engine will start in cold weather.

The high-temperature viscosity (the second number, 30 in a 5W-30 oil) provides thickness, or body, for good lubrication at operating temperatures.

Multigrade oils (for example, SAE 5W-30) provides good flow capability for cold weather but still retains thickness for high-temperature lubrication.

Monograde or single grade oils (a single number in the center of the donut, e.g. 50) are recommended for use under a much narrower set of temperature conditions than multigrade oils.

Operators should refer to their owner's manuals to select the proper viscosity oil for the ambient temperature and operating conditions at which the equipment will be used.

• Bottom - Resource Conserving and CI-4 Plus / SN Plus Designations

The bottom of the donut tells whether the oil has "Resource Conserving" properties when compared with a reference oil in an engine test or if an oil meets CI-4 Plus or SN Plus requirements.

Oils labeled as "Resource Conserving (RC)" (besides fuel saving properties as required by the former "Energy Conserving" supplemental category) requires further properties like:

• emission system protection
• turbocharger protection
• compatibility with engines operating on ethanol containing fuels, up to E-85

Widespread use of engine oils with this designation should result in an overall enhanced engine protection in the vehicle fleet as a whole.

About Lubricants

General Technical Properties  

1.   Lubricating Oil
2.   Grease

1  Lubricating Oil

Viscosity

• Indicates resistance of a liquid to flow.
• Most common unit of measurement is the metric system's unit Centistokes (cSt), measured at 40°C or 100°C. Others include Saybolt Universal Second (SSU), measured at 100°F or 210°F. 
• Oil with higher viscosity can stand greater pressure without being squeezed out of the lubricating surfaces. However, the high internal friction of the oil may offer greater resistance to the movement of the lubricating parts. An oil of lower viscosity offers less resistance to the moving parts but the oil can be easily squeezed out of the lubricating surfaces. It is therefore important to select a lubricating oil of appropriate viscosity to achieve optimum lubrication effect.
• Viscosity changes with temperature. Hence, the measuring temperature must be specified whenever the viscosity of a liquid is stated. When temperature rises, a liquid becomes less viscous. Similarly, a liquid becomes thicker when temperature drops.
• Viscosity Index (VI) is an indication of how the viscosity of a liquid varies with temperature. A high VI means the liquid does not thin out so much when temperature rises. VI improver additives that are usually high molecular weight polymers can increase the VI of lubricating oil.
• Increase in oil viscosity achieved by addition of polymers can be partially lost again through degradation of the polymer molecules by shear stress such as heavily loaded gears. Oil that can resist viscosity change due to shear are said to have high shear stability.

Pour Point

• Indicates flow characteristic at low temperature.
• Depends on the wax content of the oil.
• May be an issue for countries which encounter very low temperatures.

Flash Point

• Measures the readiness of the oil to ignite momentarily in air and is a consideration regarding the fire hazard of the oil.

Oxidation Stability

• Oxidation of oil will produce resins and sludge that may plug filters and oil passages.
• Oxidation can also produce soluble organic acids that may cause corrosion of machine parts.
• A good lubricating oil should resist oxidation.

Acidity and Alkalinity (Total Acid Number and Total Base Number)

• High acidic oil may cause corrosion of machine parts
• Most engine oils show some alkalinity due to the addition of detergent type additives and this helps to neutralize any acid formed in the oil by oxidation.
• After prolong usage, lubricating oil may contain organic acids formed by oxidation. Therefore, a measurement of the acidity of an oil can reflects its degree of oxidation.

Detergency

• Most engine oils contain detergent and dispersant additives to prevent dirty particular produced by incomplete combustion from accumulating and plating metal surface.

Anti-rust Property

• Water may seep into the lubricating system and cause rusting of machine parts.
• Rust particles can act as catalyst to accelerate the oxidation of the oil.
• Anti-rust additives can be absorbed onto metal surface and prevent moisture from coming into contact with the metal, thus preventing rusting.

Corrosion Inhibition

• Acidic materials in oil can cause corrosion of machine parts.
• Corrosion can be minimized by the additives of corrosion inhibitor that reacts with metal to form a protective layer separating the acidic materials and the metal.

Anti-foaming Property

• Foaming reduces the lubricity of oil because the air bubbles in the foam will create a barrier between the oil and the metal surface.
• Foam can also produce resistance to the movement of machine parts.
• In a hydraulic system, foam will reduce the cohesive power of the oil and cause the hydraulic pressure to drop.
• Good lubricating oil will not foam easily and can disperse foam quickly. Anti-foam additives can help to reduce the foaming tendency of oil.

Emulsification and Demulsification

• Emulsification is the homogenous mixing of oil and water.
• Some oil requires high emulsibility so that it can mix with water easily, i.e. soluble oils for metalworking industry.
• The emulsibility of oil can be improved by the addition of emulsifying agent that has strong affinity for both oil and water, thus holding the oil and water molecules together.
• Some other lubricants require good demulsibility so that water can be separated from the oil easily, e.g. Turbine oil. The demulsibility of oil can be achieved by good refining technique.

Anti-wear Properties

• Some lubricating conditions may call for extremely light oil, an oil of lower viscosity than the load-speed relationship of the machine may indicate. Under such condition, wear of the metal surfaces may occur. Anti-wear additive forms a protective coating on the metal surfaces, allowing the surfaces to slide on each other with a minimum loss of metal.

Extreme Pressure Loading Properties (EP)

• Heavy loading, extreme pressure and intense heat may cause machine moving parts to melt and weld together, hence interfering motion.
• The extreme-pressure additive in oil can react with the metal to form a compound with low melting point. The intense heat developed due to the extreme-pressure loading will be dissipated in the melting of the compound instead of welding the two metallic parts.
• EP properties are usually measured by Timken method (ASTM D 2782) or FZG Gear Machine (IP 334). 

Tackiness

• Tacky oil contain tackiness agent and will stick to the lubricating surface for a long time without being spattered. Lubricants used in textile machinery and wire ropes usually require tackiness property.

2  Grease

Grease is a semi-solid formed by the dispersion of a thickening agent in a liquid lubricants (base oil). Other ingredients imparting special properties may be included. Greases have advantage over oil in some applications because greases stay at the point of lubrication and will hardly be squeezed out. Sometimes, greases can also be used to seal up machine parts to prevent the entry of moisture and dust.

Base oil viscosity, hydrocarbon type, and volatility can influence the structure stability, lubricating quality, low and high temperature performance, and cost of grease. The thickener is the principal factor controlling water resistance, high temperature qualities, resistance to breakdown through continued use, and ability to stay in place. To a large extend, grease cost is determined by the type of thickener and other additives.

Thickener can be divided into several categories; soap-type, inorganic type and synthetic organic type.

The important characteristics of grease are as follows: -       

Penetration

• Indicates the consistency (hardness or softness) of grease.
• Measured by dropping a pointed cone into the grease and sees how far the cone penetrates into the sample.
• Different ranges of penetration are identified by National Lubricating Grease Institute (NLGI) Grade Numbers: 000, 00, 0, 1, 2, 3, 4, 5, and 6.
• Grade 000 is the softest while Grade 6 is the hardest.
• Most grease thickened with soaps become softer with increase in temperature, but some greases become progressively harder upon exposure to high temperature. 

Dropping Point

• Temperature at which the grease is fluid enough to drip. 
• Grease with a dropping point below the operating temperature would not provide proper lubricant. 
• However, the converse is not necessarily true; a dropping point above operating temperature is no guarantee of adequate lubrication since there may be change in consistency and deterioration in chemical properties of the grease at high temperatures.

Water Resistance

• Greases with thickeners soluble in water will emulsify and fluidize if come into contact with relatively large amount of water.
• Generally, calcium, lithium and aluminium soaps are highly water resistance while sodium soap greases are soluble in water.

Oxidation Stability

• Oxidation will cause the grease to harden, form varnish like films and eventually carbonize. Additives can improve the oxidation stability of grease.

Lubricating Properties

• Both the oil and the thickener in soap type grease have lubricating properties. Inorganic non-soap thickener generally does not contribute to the lubricating of grease.
• The lubricating capability of the oil depends on its viscosity and viscosity index.

Anti-wear Characteristics

• Additives may be included in a grease to promote its anti-wear properties.

Extreme Pressure Capability (EP)

• Some grease contains special additives to fortify its load carrying capability so that welding and scoring of metal can be minimized.

API Grade Classifications

API Engine Service Classifications

The American Petroleum Institute (API) engine oil classification system is a method of classifying engine oils according to their performance characteristics, and relating this to their intended type of service. It is an “open-ended” system which allows for the addition of new designations with little change to existing ones.

As of May 2020, the latest API designations are:

•   International standard  -  ILSAC GF-6,
•   For API "S" (Gasoline)  -  API SP
•   For API "C" (Diesel) -  API CK-4
•   For API "F" (Diesel)  -  API FA-4 

Information in tables below only shows API statuses which are currently licensable.

For obsolete grades, please refer to API's website.

ILSAC "GF" Standard 

API "S" - Spark-Ignition / Service Category

API "C" - Compression-ignition / Commercial Category

API "F" - Diesel F Category

For more information refer to API's website.

Latest Market Updates

API

• API Introduces Three New Gasoline Engine Oil Standards, ILSAC GF-6A, GF-6B, And API SP

• Latest API Oil Classification - API SN Plus

Technical Table

Table List

1.   SAE J300 Viscosity Grades
2.   SAE J306 Automotive Gear Viscosity Classification
3.   ISO Viscosity Grade Conversions
4.   Viscosity Ranges for AGMS Lubricant Numbers

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1  SAE J300 Viscosity Grades 

All values are critical specifications as defined by ASTM D 3244.
cP=1 mPa.s 1 cSt=1 mm2s-1

Notes:
(1) ASTM D 5293.
(2) ASTM D 4684. Note that the presence of any yield stress detectable by this method constitutes a failure regardless of viscosity.
(3) ASTM D 445.
(4) ASTM D 4683, CEC L-36-A-90 (ASTM D 4741), or ASTM D 5481.

2  SAE J306 Automotive Gear Viscosity Classification

3  ISO Viscosity Grade Conversions

4  Viscosity Ranges for AGMS Lubricant Numbers

Notes:
Viscosity ranges for AGMA Lubricant Numbers will henceforth be identical with those of the ASTM system. Oils compounded with 3% to 10% fatty or synthetic fatty oils.