Is Higher Oil Viscosity Always Better?
2 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 is limited due to poor pumpability caused by excessive viscosity. This can lead to temporary dry or semi-fluid friction. 2. Poor cooling performance. Higher viscosity oil has poorer fluidity and slower circulation speed, resulting in reduced heat dissipation from friction surfaces and potentially causing engine overheating. 3. Reduced cleaning effectiveness. Thicker oil circulates more slowly, passing through filters less frequently. This makes it harder to remove metal particles, carbon deposits, and other contaminants from friction surfaces. 4. Conversely, if oil viscosity is too low, it may not form a sufficiently thick oil film on high-temperature friction surfaces. The weaker load-bearing capacity of such thin oil films makes them prone to breakdown under pressure, leading to inadequate lubrication and increased wear.
I've been driving a ten-year-old SUV and initially thought higher viscosity oil would make the engine tougher, but it made winter starts particularly difficult. Later, after checking the vehicle manual, I realized each car has specified viscosity requirements—mine calls for 5W-30. High-viscosity oil does offer better protection at high temperatures, but its poor flow during cold starts increases wear risks. Now, I strictly use the recommended viscosity and regularly check the oil condition. Seasonal adjustments matter—consider slightly higher viscosity in hot summers, but always consult a professional repair shop to avoid engine damage. In short, higher oil viscosity isn’t always better; balancing engine protection, fuel efficiency, and climate adaptability is key.
