Fully synthetic engine oil is better. After a 10,000-kilometer test, the performance degradation of fully synthetic engine oil was less than 5%, compared to 50% for semi-synthetic oil. Here are the reasons why fully synthetic engine oil is superior: Better quality of synthetic engine oil: Synthetic engine oil offers better quality, which is noticeably evident in the following aspects: smoother cold starts, especially in northeastern regions; improved fuel efficiency; longer oil change intervals, approximately 1.5 times or more compared to conventional lubricants; extended engine lifespan and reduced maintenance frequency; and cleaner engine cylinders due to the superior detergency of synthetic oil. Wider temperature range for fully synthetic oil: Fully synthetic oil can be used in a wider temperature range and has a longer service life. For the same oil film requirements, fully synthetic oil can achieve the desired protection with lower viscosity, whereas semi-synthetic oil requires a higher viscosity to meet the same standards. In other words, under the same working conditions, fully synthetic oil can protect the engine with lower viscosity. Similarly, in the same working environment, fully synthetic oil, due to its significantly longer service life compared to semi-synthetic oil, may have a higher initial cost, but when considering the reduced frequency of oil changes, it is not much more expensive than mineral oil.
