Is Higher Oil Viscosity Always Better?
4 Answers
Higher oil viscosity is not always better. Here are the impacts of oil viscosity: 1. Difficulty in cold engine starts. If the oil viscosity is too high, oil circulation during cold starts will be slow. Although oil pressure may be high, the actual oil flow rate is low due to poor pumpability caused by high viscosity. This often leads to temporary dry friction or semi-fluid friction, which is a major cause of engine wear. 2. Poor cooling performance. Higher viscosity oil has poorer fluidity and slower circulation speed, resulting in slower heat dissipation from friction surfaces and consequently inferior cooling effects, which may cause engine overheating. 3. Inferior cleaning capability. High viscosity oil circulates more slowly and passes through filters less frequently, making it harder to remove metal particles, carbon deposits, dust and other contaminants from friction surfaces, thus reducing cleaning effectiveness. 4. Conversely, oil with too low viscosity may not form a sufficiently thick oil film on high-temperature friction surfaces. The load-bearing capacity of such thin oil films is poor and they can be easily broken under pressure, failing to provide proper lubrication and potentially increasing wear.
I used to think that higher oil viscosity was always better, but after driving for a long time, I realized that excessive viscosity makes cold starts difficult in winter, the engine struggles to turn over, and fuel consumption keeps rising. Every time I see new engine oil, I impulsively go for a higher grade, only to end up with louder noise at low speeds and poor lubrication. Later, after researching, I learned that the right viscosity is what truly matters. The numbers like 5W-30 or 10W-40 recommended by manufacturers aren’t arbitrary—they account for temperature changes. Thinner oil flows faster in high temperatures, providing better engine protection. In hot summers, high viscosity can make the engine sluggish and increase wear. My advice: don’t experiment blindly. Just follow the owner’s manual—it’s the most reliable way. Not only does it save you hassle and money, but it also extends your car’s lifespan. Remember, don’t blindly chase thick oil; matching your driving environment and vehicle type is key.
From my observation, higher oil viscosity isn't necessarily better. Excessive viscosity makes engine startup more laborious in cold environments—the sound resembles an old ox pulling a broken cart. It not only increases resistance but also wastes more gasoline. During high-temperature driving, high-viscosity oil reduces fluidity, increases internal friction, and damages components. The recommended viscosity for vehicles is carefully tested by engineers to balance cold-start performance and high-temperature protection. For instance, 5W series is suitable for northern winters, while 10W series works in southern regions. Don’t overlook driving habits—if you frequently take short trips or drive at high speeds, choosing the wrong viscosity can lead to severe carbon buildup. In short, the right viscosity ensures fuel efficiency and improves engine responsiveness. Don’t be fooled by the false sense of security from high viscosity; refer to SAE standards for selection—it saves money and is eco-friendly.
As an average car owner, I'm always worried about choosing the wrong engine oil. If the viscosity is too high, it causes real-world troubles - the engine starts as slowly as yawning, and fuel consumption becomes noticeably worse during acceleration. Different vehicle designs require different viscosity grades. Newer cars perform better with low-viscosity oils for fuel efficiency, while older vehicles may need slightly higher viscosity for stability. Your vehicle manual provides the most reliable guidance - don't make random guesses. Choose the correct viscosity grade when temperature varies significantly to avoid waste. Always check oil condition during changes to ensure proper lubrication.
