API engine oil service category is classified by the American Petroleum Institute.
It requires to clear various standards such as oxidation stability, anti-rust properties, anti-corrosion properties, anti-wear properties, anti-volatility, shearing stability and others.
The current classification is SN, and the API service symbol called "Donut" can be claimed only for the products approved by API.
【API Service for Gasoline Engine Oils】
|Wear resistance of variable valve train system||☆||☆||☆☆||☆☆☆||☆☆☆☆|
|Rust prevention performance||☆☆||☆☆||☆☆||☆☆||☆☆|
|Low volatility performance||☆||☆☆||☆☆☆☆||☆☆☆☆||☆☆☆☆|
|Deposit control at high temperature||☆||☆☆||☆☆☆||☆☆☆☆||☆☆☆☆|
|Compatibility with oil seal||☆||☆||☆||☆||☆☆|
|Compatibility with exhaust catalyst||☆☆||☆☆☆||☆☆☆||☆☆☆☆||☆☆☆☆|
|☆marks in total||16||21||28||33||37|
【API Service for Diesel Engine Oils】
|Piston cleaning efficiency||☆||☆||☆☆||☆☆☆||☆☆☆|
|Soot dispersion capability||☆||☆||☆||☆☆☆|
|Rust prevention performance||☆||☆||☆||☆||☆|
|Low volatility performance||☆||☆||☆||☆||☆☆|
|Compatibility with oil seal||☆||☆||☆||☆||☆|
|☆marks in total||6||8||9||10||14|
【API Service for Gear Oils】gear Oils, Hydraulic Fluid
|GL-1||Spiral bevel gear, worm gear and manual transmission with low face pressure and low sliding velocity.|
|GL-2||Worm gear, not applicable to GL-1 because of requirements such as load, temperature and sliding velocity.|
|GL-3||Manual transmission and spiral bevel gear having mid-range sliding velocity and loading conditions.|
|GL-4||Gears of vehicles, especially Hypoid gear, operated under high speed & low torque or low speed & high torque conditions.|
|GL-5||Gears of vehicles, especially Hypoid gear, operated under high speed & impact load, high speed & low torque or low speed & high torque conditions.|
↑Higher numbers followed after GL do not necessarily mean high quality products.
【Explaining the API Service Categorise】
ILSAC oil specification is settled by International Lubricants Standardization and Approval Committee which is formed by American and Japanese automobile manufacturers associations.
The ILSAC symbol mark, so called "Starburst", can be claimed together with API SN Donut for the products which have superior resource conserving property.
The products carrying "Starburst" are the products approved by both Japanese and American automobile manufacturers.
【SAE Viscosity Number of Engine Oils】
Categories of oil viscosity set up by the Society of Automotive Engineers （SAE）. The number followed by “W” means the viscosity grade under low temperature conditions （by CCS viscosity or Pumping viscosity; MRV） and the lower the number, the better the cold startability becomes. A number without “W” means the viscosity grade under high temperature conditions （by kinematic viscosity at 100ｰ℃） and the larger the number, the higher the viscosity becomes.
【SAE Viscosity Number of Gear Oils
and Applicable Ambient Air Temperature】