Engine oil criteria
API index
This index is announced by the American Petroleum Institute to determine the quality of motor oil. The letter S in this index stands for gasoline cars and the letter C stands for diesel cars. The other letter that is placed after these two letters, the closer to the end of the English alphabet, indicates the higher quality of the engine oil. For example, if the API index of an oil is SB, it indicates that this oil It is specific to a gasoline car, but it is not of high quality, or if this index is SN, it indicates high quality engine oil.
Viscosity index
This index is shown on the engine oil box as xxWyy. The number placed instead of xx indicates the viscosity of the oil at low temperatures or in winter. The lower this number is, it shows that the oil has a better performance in winter. The number placed instead of yy indicates the viscosity quality of the oil in summer. The higher this number indicates that this oil performs better in maintaining its viscosity at higher temperatures. In short, the lower the two numbers xx and yy, the better the oil is for cold seasons and the higher they are. It is more suitable for use at high temperatures.
گریدهای ویسکوزیته روغن موتور چیست؟
Viscosity refers to the thickness of the oil and its ability to flow at different temperatures. Common viscosity ratings are: 5W-30, 10W-40, 20W-50
Your vehicle manufacturer has specific engine oil recommendations. Choose the viscosity grade recommended in your vehicle manual for optimal performance.
Consider your climate
The letter "W" stands for winter, which indicates the oil's flow characteristics at cold temperatures, while the second number indicates the viscosity at operating temperature. The lower the number before W, the thinner the oil is when cold. The higher the number after W, the thicker the oil will be when the engine reaches operating temperature. If you live in a colder climate, choose a lower viscosity oil to ensure easy starting at low temperatures. Conversely, if you live in a hot climate, higher viscosity oils can provide better protection against heat-induced engine wear.
Consider Synthetic vs. Conventional
You also have to decide between synthetic and mineral motor oil. Synthetic oils are better known for their excellent performance under harsh conditions, lubrication and stability. However, they are usually more expensive. Mineral oil is a cost-effective option, but may not perform well in stressful situations.