United States

• The American Petroleum Institute (API), based in Washington, D.C., is the primary standards-setting organization in the United States.
  
  

API Grades

• API Grades are based on a series of groups. Group I includes basic products; Group II offers similar capabilities with higher viscosity; Group III includes oils that have been through "hydro-cracking," an additional refining process; and Group IV is for other lubricants.
  
  

Europe

• The European Automobile Manufacturers' Association, or ACEA, based on the acronym for its name in French, is based in Brussels, Belgium. It is the main standards-setting organization in Europe.
  
  

ACEA Grades

• ACEA lubricant standards are broken down to the following viscosity grades: B1 through B5, C1 through C4 and E6 through E9. Each category is for a type of engine, such as gasoline versus diesel; an older engine; or other operational advantage or limitation.
  
  

API and ACEA Differences

• In the early 1990s, European lubricant standards began to change from API's as the needs of oversees manufacturers shifted. Today, several lubricant standards fall outside of API's purview. These are referred to as original equipment manufacturer standards.