What do the specifications of motor oil mean?

[DiJesse]

Motor oil specifications indicate viscosity and quality. Taking 15W40 as an example, the 'W' stands for Winter. The smaller the number before the 'W', the better the oil's low-temperature fluidity, meaning it can be used in lower environmental temperatures. The number after the 'W' represents the oil's kinematic viscosity at 100 degrees Celsius, with higher numbers indicating higher viscosity. The '40' indicates the oil's high-temperature resistance, with larger numbers indicating better protective performance at high temperatures. Motor oil, engine oil, or engine lubricant is a substance enhanced with additives in base oil, primarily containing anti-wear additives, detergents, dispersants, and multi-grade oil viscosity index improvers. Motor oil is used for lubricating internal combustion engines.

[Sharon]

When I first got into cars, I studied motor oil grades, especially those numbers after SAE, like 5W-30 or 10W-40. The 'W' stands for winter, and the smaller the number before it (e.g., 5W), the better the oil flows at low temperatures, making cold starts easier. The larger the number after (e.g., 30 or 40), the thicker the oil is at high temperatures, providing better engine protection. Different car manuals recommend different grades, and using the wrong oil can increase wear or raise fuel consumption. Once in winter, I used 10W-40 and noticed slower starts; switching to the right oil made the engine sound smoother. Don’t skip maintenance—check the manual or ask a mechanic and change oil seasonally to keep your car performing well.

[Florence]

If you're a new car owner, understanding oil grades is actually quite simple. Those labels like SAE 5W-30 mean that SAE is the standard classification by the Society of Automotive Engineers. The number 5 before the W indicates better oil flow performance in cold weather, with lower numbers being more suitable for cold regions; the 30 after the W indicates moderate viscosity at high temperatures to protect the engine. Choosing the wrong oil may cause engine overheating or increase fuel consumption, so always follow the recommended oil change intervals in your vehicle's manual. I've found that regular oil changes can effectively extend engine life and prevent minor issues.

[JuliannaDella]

The core of engine oil grading lies in viscosity and temperature adaptability. In the SAE classification, the number before W (e.g., 0W or 5W) indicates better low-temperature flow for easier cold starts; the number after W (e.g., 30 or 40) represents high-temperature viscosity protection. Modern multi-grade oils like 5W-30 cover a wide temperature range, offering convenience and efficiency. Using higher viscosity oil increases resistance and affects fuel consumption, while lower viscosity oil poses a greater risk of wear. Always choose the manufacturer-recommended grade for reliability.

[DelLondyn]

Choosing the right oil grade can save money and be eco-friendly. Grades like SAE 10W-30 indicate fast flow at low temperatures for easier starts and moderate viscosity at high temperatures to protect the engine. Using higher viscosity oil increases engine load, fuel consumption, and costs; lower viscosity offers insufficient protection, requiring frequent oil changes and wasting resources. Matching the vehicle's recommended oil optimizes performance and reduces emissions.

[StAndrew]

Understanding oil viscosity ratings is crucial for driving safety. Numbers like 5W-30 indicate viscosity characteristics: the 5 before W shows easy cold-weather flow for freeze-proof starting; the 30 ensures stable high-temperature lubrication to prevent engine failure. Choosing the wrong grade in extreme weather may cause lubrication failure risks. Follow your vehicle manual's recommendation to check and change oil every 5,000 km for smooth operation.