What Does Engine Oil Model Number Mean?
3 Answers
Engine oil model numbers consist of two parts: classification and viscosity specifications. The oil model number typically indicates viscosity and quality. Detailed explanation: The viscosity of lubricating oil is often identified using SAE grades, where SAE stands for the Society of Automotive Engineers. More detailed information is as follows: 1. On the outer packaging of engine oil, you will often see SAE and API. SAE is the abbreviation for the Society of Automotive Engineers, and API stands for the American Petroleum Institute. The number following SAE indicates the oil's viscosity value, while the number following API indicates the oil's quality grade. 2. 10W-40 is its SAE standard viscosity value. This viscosity value first indicates that the oil is a multi-grade lubricant. The 'W' stands for WINTER, and the number before the W represents the pour point temperature, simply put, the freezing point temperature. 10W oil corresponds to a freezing point temperature of -25°C, while other common grades include 0W at -35°C, 5W at -30°C, and 15W at -20°C. The number after the W represents the oil's kinematic viscosity at 100°C, with higher numbers indicating higher viscosity. 40 means the kinematic viscosity standard at 100°C is between 12.5mm2/s and 16.3mm2/s, and it absolutely does not mean, as some folk interpretations suggest, that it can be used below 40°C. It's important to know that engine operating temperature is not necessarily determined by ambient temperature; prolonged high-RPM driving can easily raise engine temperature to 100°C, yet there are no lubricants with a 100 rating.
The oil model is represented by those alphanumeric combinations on the packaging, such as 5W-30, which actually hold significant meaning. The number preceding the 'W' indicates low-temperature performance; for example, 5W maintains fluidity even at -30 degrees Celsius, so drivers in Northeast China don't need to warm up their cars before driving. The number after the hyphen represents high-temperature performance—the higher the number, the thicker the oil. A viscosity of 40 means a thicker oil film during high-speed engine operation. This labeling follows the internationally standardized SAE standard, much like clothing sizes, helping you match your vehicle's needs. From my experience, Japanese and Korean cars perform best with 20 viscosity for fuel efficiency, while German cars are better suited for 40 viscosity to protect the turbo. Never skimp and use the wrong oil, or you'll hear the starter motor whining painfully in winter.
What do those mysterious codes on the engine oil bottle mean? They directly affect the engine's lifespan. The lower the first number, the smoother the cold start. 0W can lubricate instantly even at -40°C, so you won't have to worry driving in Alaska. The latter number represents viscosity at high temperatures. Older cars with more wear should use 40-grade oil, while newer engines perform better with lighter 20-grade. It's like choosing the right blood type for the heart—if the manufacturer's manual specifies 5W-30, don't experiment with 5W-40. Using the wrong oil can cause sludge buildup, clog oil passages, and lead to knocking noises at high RPMs. I've personally seen a BMW develop VANOS system issues due to incorrect oil, and the repair bill was enough to make your hair stand on end.
