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LO 10-2 Describe the purpose, properties, function, composition, types, and applications of diesel engine lubricating oils

1. Purpose and Function of the Lubrication System

1.10. The American Petroleum Institute Service Symbol

LO 10-02: Describe the purpose, properties, function, composition, types, and applications of diesel engine lubricating oils.

 

The American Petroleum Institute Service Symbol
The API service symbol and certification mark, which resembles a donut, identifies the performance standards of engine oils used in gasoline- and diesel-powered vehicles Figure 18. Engine oil carrying API designations can only be certified after specialized testing to determine whether they meet minimum API standards. Only certified oils meeting minimum API criteria are permitted to carry the API service symbol.

The API donut symbol is divided into three parts:

  • The top half designates the oil’s performance standard set by the API test criteria.
  • The center identifies the oil’s SAE viscosity rating.
  • The bottom half is the API certification mark.

Gasoline engines may carry a starburst symbol, whereas diesels do not. In gasoline engines, the mark or starburst symbol indicates whether the oil has demonstrated energy-conserving properties in a standard test in comparison to reference oil. The use of friction-reducing additives, such as graphite, molybdenum disulfide, or other suspended oil additives, provides energy-saving enhancements to the oils.

   Fig10_18

FIGURE 10-18: The API service symbol and certification mark. It identifies the performance standard (1), the SAE viscosity rating (2), and the energy-conserving or other special properties (3).

 

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