![]() In fact, when multi-grades were initially developed, they were frequently described as all-season oil. This enables one type of oil to be used all year. The idea is to cause the multi-grade oil to have the viscosity of the base grade when cold and the viscosity of the second grade when hot. These additives are used to make the oil a multi-grade motor oil, though it is possible to have a multi-grade oil without the use of VIIs. To address this issue, manufacturers began adding special polymer additives called viscosity index improvers (VIIs) to the oil. The difference in viscosities for most single-grade oil is too large between the extremes of temperature, meaning that in cold weather it would be difficult to start the engine as the oil was too thick to crank. However, the temperature range the oil is exposed to in contemporary passenger cars can be wide, ranging from cold temperatures in the winter before the vehicle is started up to hot operating temperatures when the vehicle is fully warmed up in hot summer weather. For example, a lawnmower may require SAE 30 monograde engine oil that must meet the SAE 30 requirements. The original viscosity grades were all single grades such as SAE 30, measured at 100 ☌ (212 ☏) and with higher number meaning higher viscosity. The higher numbers of a gear oil (e.g., 75W-140) does not mean that it has higher viscosity than an engine oil 20W-50. The SAE has a separate viscosity rating system for gear, axle, and manual transmission oils, SAE J306, which should not be confused with engine oil viscosity. This standard is commonly used throughout the world, and standards organizations that do so include API and ILSAC, and ACEA. Key parameters for engine oil viscometrics are the oil's kinematic viscosity, its high temperature-high shear viscosity measured by the tapered bearing simulator, and low temperature properties measured by the cold-cranking simulator and mini-rotary viscometer. ![]() SAE J300 is a standard that defines the viscometric properties of mono- and multigrade engine oils, maintained by SAE International. Standard for engine oil Different brands and grades of bottled motor oil at a store
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |