How to Distinguish Engine Oil Viscosity Grades?
4 Answers
Engine oil viscosity grades are distinguished as follows: The viscosity grade of the oil is indicated on the oil bottle. 'SAE' represents the viscosity grade of the oil. The number before 'W' indicates the winter viscosity—the smaller the number, the lower the viscosity. The number after 'W' indicates the summer viscosity—the larger the number, the higher the viscosity. The functions of engine oil include: 1. Lubricating between pistons and cylinders, and between main shafts and bearings; 2. Carrying heat back to the oil tank and dissipating it into the air to help the radiator cool the engine; 3. Transporting carbon deposits, sludge, and worn metal particles from engine components back to the oil tank through circulation, cleaning contaminants from the working surfaces of parts; 4. Forming a seal between piston rings and pistons to reduce gas leakage and prevent external contaminants from entering; 5. Providing rust and corrosion protection; 6. Cushioning the load on pistons, piston skirts, connecting rods, and crankshaft bearings; 7. Reducing the coefficient of friction.
The classification of oil viscosity grades primarily depends on the numerical combinations in the SAE standard. For example, in a grade like 5W-30, the number before 'W' indicates low-temperature fluidity—the smaller the number, the smoother the cold starts in winter. For instance, when I drive my old sedan in the north, using 0W-20 makes it easy to start the engine. The number after 'W' represents high-temperature viscosity—the larger the number, the better the engine protection under high summer temperatures. My car's manual recommends 10W-40, but based on my city's climate, I choose 5W-30 for a balance between fuel efficiency and protection. It's important to note that different vehicle models have different requirements; SUVs or high-displacement vehicles might need higher numbers like 20 or 40 to prevent wear. Choosing the wrong grade can reduce fuel efficiency or shorten engine life. After learning this through online manuals and labels, I save money on oil changes and ensure more reliable maintenance. Every time I change the oil, I check these numbers to avoid issues, especially during seasonal changes between extreme cold and heat, to protect my beloved car.
To distinguish engine oil viscosity grades, just look at the SAE numbers on the packaging, which are set by international standards. A lower number before the 'W' indicates better low-temperature performance—for example, 5W can start smoothly at zero degrees. A higher number after the 'W,' like 30, means the oil is thicker at high temperatures to prevent leaks. Having worked on DIY car repairs for years, I've found that shaking the oil bottle to feel its flow speed also works—oils with lower low-temperature numbers flow easily but burn off faster, while those with higher high-temperature numbers are thicker and heat-resistant but consume more fuel. New cars perform best with low-viscosity oils like 0W-20 for fuel efficiency, while older cars can use 10W-40 for better component protection. Always check your vehicle's manual before making changes—I use a viscosity tester to confirm my choice and regularly inspect to avoid increased engine noise. This knowledge has helped me save on maintenance costs with DIY care, and fellow car enthusiasts find it practical and appreciate the tip.
Understanding oil viscosity grades isn't actually difficult, the numbers in the SAE code are key. A low number before W like 5 is good for cold starts, while a higher number after W like 30 protects the engine in hot weather - this fundamental principle I've mastered through years of driving. In the past oils had single numbers, but today's dual ratings are more precise - you must choose the matching type based on your vehicle model, with SUVs often needing high 40 viscosity to prevent leaks. From experience, older engines with more wear perform better with post-20 numbers. Remembering these numerical differences prevents wasteful frequent oil changes - this knowledge has protected my engine and extended its lifespan.
