What is the difference between semi-synthetic oil and fully synthetic oil?
2 Answers
Semi-synthetic oil and fully synthetic oil are two classifications of engine oil. The following are the specific differences between them: 1. Different base oils: Semi-synthetic oil uses Group III base oil; fully synthetic oil is a mixture of Group III, IV, and V base oils. 2. Different replacement intervals: Semi-synthetic oil should be replaced every six months or 7,500 kilometers during use; fully synthetic oil should be replaced every year or 10,000 kilometers during use. 3. Different applicable temperatures: Fully synthetic oil has a wider range of operating temperatures. In the same working environment, fully synthetic oil can protect the engine with a lower viscosity, while semi-synthetic oil has relatively higher requirements for use.
Semi-synthetic oil is a blend of mineral oil and synthetic base oil, offering lower cost but average performance. Fully synthetic oil consists entirely of artificially synthesized high-purity base oils, featuring uniform molecular structure, strong oxidation resistance, excellent low-temperature fluidity, and superior high-temperature stability. From my experience, fully synthetic oil is more suitable for turbocharged engines or performance cars, especially providing smoother cold starts in winter and reducing cold-start wear. However, semi-synthetic oil is sufficient for regular commuter cars, being about one-third cheaper, though it requires changes around every 5,000 kilometers, while fully synthetic can last 8,000 to 10,000 kilometers. In the long run, the cost difference isn't significant. Don't overlook the quality of the oil filter either—even the best oil is wasted if paired with a low-quality filter.
