The Difference Between Semi-Synthetic and Synthetic Engine Oil?
2 Answers
Semi-synthetic and synthetic engine oils mainly differ in the following aspects: 1. Different base oils: Semi-synthetic engine oil uses Group III base oil; full synthetic engine oil is a blend of Group III, IV, and V base oils. 2. Different replacement intervals: Semi-synthetic engine oil should be replaced every six months or 7,500 kilometers during use; full synthetic engine oil should be replaced every year or 10,000 kilometers during use. 3. Different applicable temperatures: Full synthetic engine oil has a wider temperature range. In the same working environment, full synthetic oil can achieve engine protection with a lower viscosity, while semi-synthetic engine oil has relatively higher usage requirements.
Semi-synthetic oil is made from mineral oil blended with synthetic additives, suitable for daily driving but with average performance. Like I've used it for several years, it performs decently at moderate temperatures, but starts slowly in winter and offers less engine protection than full synthetic when overheating in summer. Full synthetic oil is purely artificially synthesized, with purer base oils that can withstand extreme temperature fluctuations, maintaining stable engine performance and longer lifespan. Though more costly, it's worth it, especially for drivers frequently taking long trips or facing harsh weather, saving the hassle of frequent oil changes. I've also found synthetic oil reduces sludge buildup and extends engine life—despite higher initial investment, it's more economical long-term. If budget is tight, semi-synthetic is an option, but for reliability seekers, full synthetic is superior. Regularly check oil level and color to prevent degradation from harming engine health.
