BMW cars have their engine oil changed in the engine. The main functions of engine oil are as follows: 1. Lubrication and friction reduction: Forms an oil film on the surfaces of two sliding components to prevent friction during operation, ensuring smooth functioning of the parts. 2. Auxiliary cooling: The engine generates high temperatures during operation, and when the oil reaches these areas, it absorbs heat and carries it away, aiding in the dissipation of heat from the components. 3. Cleaning: It can carry carbon deposits, sludge, and worn metal particles from engine parts back to the oil tank through circulation, flushing away contaminants generated on the working surfaces of the parts via the flow of the lubricating oil. 4. Sealing and leakage prevention: The oil can form a seal between the piston rings and the piston, reducing gas leakage and preventing external contaminants from entering. 5. Rust and corrosion prevention: The lubricating oil adheres to the surfaces of parts, preventing contact with water, air, acidic substances, and harmful gases. 6. Shock absorption: When the pressure at the engine cylinder port rises sharply, suddenly increasing the load on the piston, piston skirt, connecting rod, and crankshaft bearings, the lubrication transmitted through the bearings helps cushion the impact load. Points to note when changing engine oil include: Engine oil is extremely important for engine operation as it carries the dual functions of lubrication and heat dissipation. Therefore, do not let the oil level fall too low. However, overfilling (exceeding the upper limit on the dipstick) can have adverse effects. Excessive oil increases the rotational resistance of the crankshaft, reduces engine output power, and the surplus oil may enter the combustion chamber, leading to oil burning, blue smoke emissions, and increased fuel consumption. The residue from burned oil (mainly composed of carbon, which is very hard) can accumulate on the combustion chamber walls, reducing the chamber's volume and thus lowering the engine's compression ratio. It can also accelerate wear on the cylinders and pistons, shortening the vehicle's lifespan. When adding oil, it is advisable to keep the level slightly below the mark on the dipstick. Additionally, factors such as oil type, season, climate, engine displacement, and technical performance should be considered. It is best to choose a professional automotive maintenance center where experts can carefully assess the vehicle, select the appropriate oil, and perform meticulous maintenance procedures to prevent potential faults.
