Is 5W30 Semi-Synthetic or Fully Synthetic?

[McLyla]

5W30 refers to a grade of engine oil and is not related to whether the oil is fully synthetic or not. In 5W30, the number 5 indicates that the oil is suitable for temperatures above -25 degrees Celsius. The smaller the number before the W, the better the low-temperature fluidity. W stands for winter, and the larger the number after it, the higher the viscosity, which provides better protection for the engine at high temperatures. Differences between fully synthetic and semi-synthetic oils: Base oil differences: Fully synthetic oil is a blend of Group III, IV, and V base oils, while semi-synthetic oil uses Group III base oil. Replacement intervals differ: Fully synthetic oil should be replaced once a year or every 10,000 kilometers, whereas semi-synthetic oil should be replaced every six months or every 7,500 kilometers. Applicable vehicle conditions vary: Fully synthetic oil is more commonly used in turbocharged engines and high-end luxury vehicles, while semi-synthetic oil is more suitable for economical, small-displacement vehicles designed for smooth driving. Additive differences: Synthetic oil contains higher TBN (Total Base Number) additives, resulting in a longer oil lifespan and better engine cleaning. Semi-synthetic oil has lower TBN additive content, leading to shorter maintenance intervals and a higher tendency to produce sulfurized ash. This indirectly contributes to the high stability of synthetic oil, which is composed of premium base oils and high-quality additives. It has minimal fluctuations, greater stability, and reduced friction, making it less susceptible to temperature variations.