Can fully synthetic engine oil be changed every 15,000 kilometers?
3 Answers
Fully synthetic engine oil should not be changed every 15,000 kilometers. The recommended replacement interval for fully synthetic oil is one year or 10,000 kilometers. Currently, engine oils on the market can be categorized into mineral oil, semi-synthetic oil, and fully synthetic oil. Among these, fully synthetic oil is the most expensive, has the widest applicable temperature range, and offers the best performance. The primary reason fully synthetic oil outperforms mineral and semi-synthetic oils lies in its superior base oil and additives. The base oil is the core indicator determining the quality and performance of an engine oil. Fully synthetic oil consists entirely of synthetic components. Synthetic oil is chemically engineered, offering significantly better performance and quality compared to mineral oil refined from petroleum. It more effectively meets engine requirements and provides superior protection. In addition to fully synthetic oil, there are semi-synthetic and mineral oils. Semi-synthetic oil is recommended for replacement every 7,500 kilometers or 8 months, while mineral oil requires maintenance every six months or 5,000 kilometers. Mineral oil is more commonly used in older vehicles. Its relatively higher viscosity makes it ideal for older engines with wear and larger gaps, as it can fully coat and effectively protect the engine.
Well, after driving for so many years myself, I think it's theoretically feasible to change full synthetic oil every 15,000 kilometers, but it doesn't guarantee suitability for everyone. I'm the kind of person who enjoys researching car maintenance, and synthetic oil indeed performs excellently, with good high-temperature resistance and oxidation stability, theoretically supporting long oil change intervals. However, the key is to consider your car model and driving conditions, such as what the manual requires, whether you drive in congested areas, or if the weather is hot and humid or dry and cold. When I drive more on highways, the oil consumption is lower, but in city traffic with frequent congestion, the oil degrades faster, and it might deteriorate significantly before reaching 15,000 kilometers. Also, it depends on the brand and quality of the oil; high-certification premium oils are more durable. I recommend regularly checking the oil level and color—if it turns black or has impurities, change it immediately; otherwise, delaying it increases the risk of engine carbon buildup and wear, which can be very expensive to repair. Overall, 7,500 to 10,000 kilometers is a safer point, balancing safety and cost-effectiveness.
I have a car that uses full synthetic oil, and I drive it frequently, always thinking about saving money by extending the oil change interval. Once, I pushed it to 14,000 kilometers, and I noticed the engine noise got louder, fuel consumption increased, and when I checked, the oil was extremely dirty—it scared me. So, changing oil at 15,000 kilometers isn’t impossible, but you have to consider real-world factors. In my city, traffic is congested with frequent stops and starts, which accelerates oil oxidation and degradation. If you mostly drive on highways, the wear is less severe. Also, the vehicle manual’s recommended interval is the baseline—don’t blindly follow online advice. My friend didn’t follow the manual for oil changes, and his engine ended up burning out, costing thousands in repairs. Now, I check the oil every 8,000 kilometers and change it immediately if anything seems off. Saving on one oil change might lead to a heap of trouble—always weigh the pros and cons with safety as the top priority.
