Viscosity is the thickness of oil, it also shows how easy the oil to flow and to behave and misbehave like OIL. There where the SAE rating come in.
The API Starburst identifies engine oils recommended for a certain application, such as "For Gasoline Engines." To carry this symbol on the container, the oil must satisfy the most current requirements of the International Lubrication Standardization and Approval Committee minimum performance standard for that application.
The service rating indicates that oil's performance properties, such as its ability to deal with extremes of heat, to minimize harmful deposits or contribute to reduced oil consumption.
The ratings are expressed as a pair of letters:
- gasoline engines the first letter is "S" for spark. Also, "C" for Diesel 's compression.
- The second letter�beginning with "A" ...till the current classification, "M," indicates the performance rating.
It is significant to remember that each succeeding, or higher, performance rating includes all the capabilities of all those that have gone before it. Therefore, the current rating, "M," will work for any automobile (petrol) engine on the road.
The following Category/Status/Service list indicates the performance ratings:
SM � Current � For all automotive engines presently in use.
SL, SJ � Current � For 2004, 2001 and older automotive engines.
SH, SG, SF, SE, SD, SC, SB, SA � Obsolete � For 1993 and older engines.