What is the difference between fully synthetic and semi-synthetic engine oil?

[CaydenFitz]

The differences between fully synthetic and semi-synthetic engine oil are: 1. Different replacement cycles: Fully synthetic oil should be replaced once a year or every 10,000 kilometers during use; semi-synthetic oil should be replaced every six months or every 7,500 kilometers during use. 2. Different applicable vehicle conditions: Fully synthetic oil can be used under various harsh conditions or when pursuing engine maintenance; semi-synthetic oil is more suitable for economical small-displacement vehicles with smooth driving. 3. Different additives used: Fully synthetic oil uses additives with high TBN content, making the oil last longer and clean the engine; semi-synthetic oil uses additives with low TBN content, shortening the oil maintenance cycle and producing sulfide ash.