What are the Selection Criteria for Engine Oils?

The characteristics of the engine are taken into account in the selection of an engine oil for internal combustion engines. Lubricant manufacturers apply three key criteria in producing the oil suitable for the relevant engine. These 3 key selection criteria are as follows:
  1. Viscosity class
  2. Performance level
  3. OEM approval (Approval of the Original Equipment Manufacturer)
In addition to these, auxiliary criteria (base oil quality, ash rate, viscosity index, pour point, evaporation loss, fuel economy, etc.) are also important.

Viscosity class is basically defined based on the SAE (Society of Automotive Engineers) norms. (SAE J300)
 

There are some automotive associations and authorities that determine Performance Levels. These are as follows;
 
  • API: American Petroleum Institute
  • ACEA: European Automobile Manufacturers' Association
  • JASO: Japanese Automotive Standards Organization
  • ILSAC: International Lubricant Standardization and Approval Committee
 
Apart from all these, some globally known vehicle manufacturers (OEM) establish their own specifications and classify engine oils with their test methods.