What letter represents fully synthetic engine oil?
1 Answers
Fully synthetic engine oil does not have a letter designation. The API of engine oil only represents the oil grade, and there is no necessary connection between the oil grade and whether it is fully synthetic. For example: SN grade is currently a higher grade, but SN grade does not necessarily mean it is all fully synthetic engine oil; there are also semi-synthetic oils. There are two designations for engine oil: one is SAE, and the other is API. SAE is used to indicate the viscosity of the oil, while API is used to indicate the grade of the oil. API is the abbreviation for the American Petroleum Institute, indicating the quality level of the oil. The API designation consists of two letters: the first letter, if it is S, indicates gasoline engines, and if it is C, it indicates diesel engines.