Is a Higher or Lower Oil Viscosity Index Better?
3 Answers
Neither too low nor too high oil viscosity is ideal; the correct choice should be based on the maintenance manual and your actual situation. The viscosity of the oil should be selected according to the engine's own condition and the ambient temperature. If the internal parts of the engine have small gaps, a lower viscosity (thinner) oil is needed; conversely, larger gaps require a higher viscosity (thicker) oil. Additional information: 1. Although many car owners hope to have both "lower high-temperature low-shear kinematic viscosity" and "higher high-temperature high-shear kinematic viscosity," it is difficult to find oil models with very high high-temperature high-shear viscosity among low kinematic viscosity oils. For American and Japanese cars, which are moving toward greater precision under the general trend of energy conservation and environmental protection, 5W30 is often considered the ideal oil viscosity for engine warm-up. For these engines, the difference between 2.8cP and 3.5cP oil film thickness is generally negligible. 2. Besides the impact of these three viscosities on oil performance, another indicator has a killer-level influence on the oil's service life: the total base number (TBN). TBN represents the total number of alkaline elements in the oil and is an important indirect indicator of the content of cleaning and dispersing additives. Since gasoline combustion in the cylinder produces a small amount of sulfides that remain on the cylinder wall surface, and sulfides themselves are weakly acidic, manufacturers add "weakly alkaline cleaning dispersants" to the oil formulation to enhance the oil's cleaning effect. TBN is used to indicate the remaining content of cleaning dispersants in the oil, an important indicator often used to measure how much mileage is left in the oil's service life. At the same time, the rate of decline in TBN can also be used to assess combustion quality. Those oils that need to be replaced every 5,000 kilometers generally refer to high-viscosity mineral oils. From this, it is evident how significant the advantages of full synthetic oils are!
There's no absolute good or bad when it comes to oil viscosity index - it depends on your vehicle and usage. As someone who drives long distances year-round across various regions, I've found that higher viscosity index oil provides more stable engine performance in extreme summer heat or winter cold, with quicker starts, better lubrication, and reduced wear. However, if you drive an older, simpler vehicle for short trips, lower viscosity might be more suitable and cost-effective. Always consult your manual or mechanic before switching oil brands. Most modern vehicles now recommend higher viscosity index oils, especially synthetics, for better temperature adaptability. Remember, wrong choices can accelerate engine aging and increase fuel consumption. Pay close attention to your oil condition during regular maintenance.
I always struggle with this issue when changing engine oil. As an average car owner, higher viscosity index oils are more suitable for daily use in variable weather conditions – for instance, they provide easier cold starts in northern winters while maintaining good protection in summer. Lower viscosity index oils may work fine for gentle driving in warm conditions, but aren't generally recommended. Having tried different oils, I find synthetic oils with higher viscosity offer quieter operation and better durability. The choice really depends on your location's climate and driving habits. Never ignore your vehicle manual's recommendations and change oil blindly. Using quality oil long-term is crucial for extending your car's lifespan. Here's a tip: oil brands vary significantly, so selecting the right specification is key.
