How to Distinguish Between High and Low Oil Viscosity?
2 Answers
The method to distinguish between high and low oil viscosity is: The oil viscosity grade is indicated on the oil bottle, with 'SAE' representing the oil's viscosity rating. 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 are: 1. Lubricating between the piston and cylinder, and between the main shaft and bearing; 2. Carrying heat back to the oil tank and then 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 dirt generated on the working surfaces of parts; 4. Forming a seal between the piston ring and piston to reduce gas leakage and prevent external contaminants from entering; 5. Preventing rust and corrosion; 6. Absorbing the load on the piston, piston pin, connecting rod, and crankshaft bearings; 7. Reducing the friction coefficient.
I remember being confused by motor oil grades when I first bought my car, so I consulted an experienced mechanic. Now when selecting oil, I focus on two key numbers: The lower the number before W, the better for cold starts - like 0W can handle -35°C extreme cold, while 5W suits around -30°C. The number after W (e.g. 30/40) actually determines high-temperature protection. A simple test is dropping used oil on paper to observe spread - slow-spreading thick oil rings indicate higher viscosity. Actually, checking your vehicle manual is most reliable - German cars often use 40 viscosity, while Japanese models mostly use 20. Never mix oils randomly - my neighbor once added high-viscosity oil improperly, resulting in engine dry grinding during cold starts and a sharp fuel consumption increase.
