![]() ![]() The first number indicates the viscosity of the oil at a cold temperature, while the second number indicates the viscosity at operating temperature. The polymers allow the oil to have different weights at different temperatures. Multi-weight oils (such as 10W-30) are a new invention made possible by adding polymers to oil. ?The centistoke rating is converted into the SAE weight designation using a chart like the one shown on the Superior Lubricants Web site. With petroleum oils, viscosity is now commonly reported in centistokes (cSt), measured at either 40?C or 100 ?C (ASTM Method D445 - Kinematic Viscosity). Since viscosity varies inversely with temperature, its value is meaningless unless accompanied by the temperature at which it is determined. The higher the value, the more viscous the fluid. Viscosity is ordinarily expressed in terms of the time required for a st?andard quantity of the fluid at a certain temperature to flow through a standard orifice. According to the Automotive and Industrial Lubricants Glossary of Terms: The standard unit used to measure viscosity is the centistoke (cSt). Honey has a very high viscosity - it is thick and gooey. Water has a very low viscosity - it is thin and flows easily. A thin oil has a lower number and flows more easily, while thick oils have a higher number and are more resistant to flow. The viscosity grade (for example, 5W-30) tells you the oil's thickness, or viscosity. ?The API service rating is a two-letter rating that tells you the type of engine the oil is meant for (gasoline or diesel) and the quality level. ![]() "Energy Conserving" indicator (it either is or it isn't) On every bottle of motor oil there is a seal that gives you three pieces of information:ģ. ![]()
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