What is engine oil made of?
2 Answers
Engine oil is composed of base oil and additives. If it is mineral oil, the base oil is refined from petroleum; if it is fully synthetic oil, the base oil is artificially synthesized. The following are the functions of engine oil: 1. Lubrication and friction reduction: A layer of oil film is formed on the surfaces of two sliding components to prevent friction during operation, ensuring smooth movement of the components. 2. Cleaning and dispersion: High-quality engine oil can flush away dirt on the surfaces of parts through its flow, adsorb tiny metal fragments in the engine, and then scrape them into the oil pan via the piston oil ring. 3. Cooling: The engine generates high temperatures during operation. When the oil reaches the operating parts, it absorbs heat and carries it away, assisting in the heat dissipation of the components. 4. Sealing and leak prevention: An oil film forms a seal between the piston rings and the piston, preventing combustion exhaust gases from entering the crankcase. 5. Rust and corrosion prevention: High-quality engine oil adheres to the surfaces of parts, preventing contact with air, acidic substances, and harmful gases, thereby protecting the engine from corrosion by the atmosphere and water.
The formulation of engine oil is actually quite sophisticated. Over the years of repairing cars, I've handled hundreds of types of engine oil, which mainly consist of two components: base oil and additives. Base oil accounts for 70%-90% of the composition. For example, mineral oil is directly refined from crude oil, semi-synthetic oil is a blend of mineral and synthetic components, while full synthetic oil is entirely composed of artificially synthesized molecules, making it more stable. The remaining 10%-30% consists of additives, which are the core of the oil. These include anti-wear agents to reduce engine friction, detergents to prevent sludge buildup, and antioxidants to extend the oil's lifespan. I once encountered a car owner who used cheap, low-quality oil to save money, but the lack of sufficient detergents led to clogged oil passages, resulting in repair costs three times higher than the money saved on oil. In the end, choosing engine oil is like selecting skincare products—you need both basic lubrication and functional ingredients.
