What Do the Parameters of Engine Oil Represent?
3 Answers
Here are the meanings of engine oil parameters: 1. Oil classification: Engine oil starting with "S" is specifically for gasoline engines, with a total of 13 quality grades from SA to SP. Diesel engine oil starts with the letter "C", and the grades are CA, CB, CC, CD, CE, CF, CF-4, CG-4, CH-4, CI-4, CJ-4. Whether it's a gasoline or diesel vehicle, each increment in the oil quality grade letter indicates superior performance compared to the previous one. 2. Oil viscosity specifications: Different types of engine oil have their own characteristics. For example, 15w40 oil: (1) The oil model containing the letter "W" stands for winter. "15" indicates the viscosity of the oil under low-temperature conditions. The smaller the number, the stronger the oil's cold resistance, making it easier to start the engine even at very low temperatures. (2) The last number "30" represents the kinematic viscosity standard at 100 degrees Celsius (between 9.3mm2/s and 12.5mm2/s).
I've been driving for almost 30 years, and the parameters of engine oil are not just written randomly. You need to understand how to choose oil to keep the engine running smoothly. Symbols like 5W-30: the 5W represents the viscosity during cold starts in winter—the smaller the number, like 0W, means the oil won’t clump in freezing weather, making it easier to start. The 30 indicates the protection capability at high temperatures—the larger the number, the thicker the oil, which is suitable for high speeds or hot weather. API standards like SN or SP indicate the oil’s quality grade—the newer the number, the cleaner and more energy-efficient the oil. Choosing the wrong parameters might cause the car to fail to start or drastically increase fuel consumption, especially in northern winters where high W-number oil can make the engine rattle. I’ve also seen cases where the wrong oil caused the engine to overheat during long summer drives, wearing out quickly. So, you must consider regional weather and driving habits when selecting oil—don’t switch oils carelessly. Follow the manual’s recommendations to keep the engine durable and cost-effective.
As a car enthusiast, engine oil specifications are one of the details I pay most attention to. SAE grades like 0W-20 serve as the oil's ID card - the number before W indicates cold-weather fluidity (lower numbers flow better in cold starts), while the number after W represents high-temperature viscosity (higher numbers like 40 ensure protection during aggressive driving). API standards like GF-6 focus more on cleanliness and fuel efficiency, reducing engine deposits. This significantly impacts performance cars - wrong oil choice can cause insufficient lubrication during hard acceleration, accelerating wear. My tests show low-viscosity oils can save about 10% fuel in city driving, but long-distance highway trips require higher viscosity for stability. New specifications also accommodate turbocharged systems - choosing the right oil makes throttle response sharper and extends engine life.
