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SAE: Society of Automotive Engineers - The SAE J 300 norm defines what is called a "Grade of viscosity" for each lubricant. Ex : S.A.E. 40 (summer viscosity grade). The higher the number, the more the oil will preserve viscosity when subjected to heat.
| In the case of city or sport driving, or when ambient temperatures are high, the engine is subjected to high temperatures. It is important to use an oil that remains sufficiently viscous under heat to protect the engine.
When the engine is cold, on the contrary, oil has a tendency to thicken. It is important then that it remain fluid, even at low temperatures in order to flow throughout the engine and protect mechanical parts and to aid in starting. Cold viscosity is signalled in S.A.E. norms by a "winter viscosity grade". Ex : S.A.E.10W The number which signals the winter viscosity grade is always followed by a "W" (for "winter")
The smaller the number, the more the oil will remain fluid in cold weather or at vehicle start.
Monograde oils are generally used when the running temperatures do not vary greatly (or for specific uses).
Multigrade oils offer a winter and summer grade simultaneously.
Ex : S.A.E. 10W 40
Where : 10W = Winter grade
40 = Summer grade
A multi-grade oil is less sensitive to temperature. | |
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