تاپیک جامع روغن موتور ها - Engine Oils
API Gasoline Engine Classification
SD : For the gasoline engines of passenger cars and trucks dating from 1968 to 1970. An SC oil should offer protection against the formation of deposits at high (detergency) and low (dispersion) temperatures. Additional protection is also required against wear and rust.
SE : For the gasoline engines of passenger cars and trucks dating from 1971. The SE oils can replace SC oils. Compared to the preceding category, SC oils offer better resistance to oxidation and the formation of "cold sludge" at low temperatures. The engine is also better protected against rust.
SF : For the gasoline engines of passenger cars and some trucks dating from 1980. SF oils can replace SE and SC oils. SF oils are better than SE oils as concerns resistance to ageing and protection against wear.
SG : For gasoline engines of passenger cars and some trucks dating from 1989. SG oils can replace SF, SG, CC, SE or SE/CC oils. SG oils have better results than SF oils in resisting the formation of deposits, protection against wear and resistance to corrosion.
SH : Same as SG but more stringent test conditions.
SJ : At SH level, but developed in accord with the API certification system following multiple test criteria.
S.A.E. Norm
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 multigrade oil is less sensitive to temperature.
