The viscosity of engine oil can be comprehensively determined through various methods. For example, in "5W-30", the smaller the number before "W" (such as 0W or 5W), the better the low-temperature fluidity, indicating suitability for cold-start protection in frigid environments; the larger the number after "W" (such as 30 or 40), the higher the high-temperature viscosity, ensuring more stable lubrication under high temperatures. In routine checks, you can observe the flow rate by dropping oil onto a clean, flat surface: high-viscosity oil flows sluggishly while low-viscosity oil spreads rapidly. Professional servicing employs viscometers for precise measurements, but vehicle owners should prioritize the viscosity specifications recommended in their owner's manual, as different engine designs have distinct oil requirements. Additionally, fresh engine oil typically appears light-colored and transparent; darkening or cloudiness may indicate the need for replacement, though this visual assessment should not substitute for viscosity evaluation. For instance, regions with consistently high temperatures may opt for slightly higher high-temperature viscosity grades, but avoid excessively high viscosity that could increase engine drag. Adhering to scheduled viscosity-appropriate oil changes as specified in the manual is crucial for prolonging engine lifespan.
