Is 5W-40 Oil Fully Synthetic?
2 Answers
5W-40 is just the viscosity grade of engine oil and cannot determine whether it is fully synthetic. Fully synthetic oil is usually indicated on the outer packaging. Mineral oil can also be labeled as 5W-40, semi-synthetic oil can be labeled as 5W-40, and fully synthetic oil can also be labeled as 5W-40. Below is an introduction to these types of engine oils: Mineral Oil: Mineral oil is the residue left after refining gasoline and heavy oil from petroleum. It is actually a natural oil with more impurities, cheaper compared to semi-synthetic and fully synthetic oils, has poorer lubrication for the engine, and a shorter service life. Semi-Synthetic Oil: Semi-synthetic oil is between mineral oil and fully synthetic oil. It contains a large number of anti-corrosion additives to improve the stability and oxidation resistance of the oil. Fully Synthetic Oil: Fully synthetic oil is the highest quality and most durable among these three types of engine oils, and it is also the most expensive. Generally, it can be used in passenger cars for 10,000 to 12,000 kilometers without deteriorating.
As a car owner, I once got confused when choosing engine oil. 5W-40 is actually the viscosity rating of the oil. For example, the 'W' stands for Winter, indicating low-temperature startup viscosity, and '40' represents high-temperature viscosity. It does not define whether the oil is fully synthetic or semi-synthetic. Fully synthetic oil is entirely composed of chemically synthesized oils and additives, offering better performance but at a higher cost. On the other hand, 5W-40 can be mineral oil, semi-synthetic, or fully synthetic, depending on the label or brand specifications. When I last changed my oil, I specifically chose a well-known brand's fully synthetic 5W-40 because it provides quick cold starts and better fuel efficiency. However, if you drive in hot and dusty areas, a semi-synthetic 5W-40 might be sufficient and more cost-effective. In short, when selecting engine oil, don't just look at the numbers—check the packaging for the clearly stated type.
