What are the effects of high oil viscosity on the engine?
3 Answers
High oil viscosity affects the engine in the following ways: Excessive oil viscosity increases the resistance during engine operation, leading to higher fuel consumption. It also makes it harder to form a protective oil film on mechanical surfaces, resulting in increased noise and accelerated wear of engine components during high-speed operation. As the engine operates, internal temperatures rise, causing the oil to thin. Therefore, selecting the appropriate oil viscosity is crucial for effectively reducing engine wear. Naturally aspirated engines can typically use 30-weight oil, turbocharged engines may opt for 40-weight oil, while large-displacement, high-revving, high-performance naturally aspirated engines might require 60-weight oil.
Using high-viscosity engine oil can make the engine work harder. I've used oil with higher viscosity before and clearly felt the car accelerate slower, with increased fuel consumption—meaning more trips to the gas station and higher costs each month. On cold mornings, starting the engine feels like it's wrapped in a thick coat, with poor oil flow, increasing wear on pistons and crankshafts, and shortening engine life. Although high viscosity provides better protection at high speeds, the overall drawbacks outweigh the benefits. It's recommended to follow the manufacturer's standard viscosity, such as 5W-30, and avoid arbitrarily using thicker oil. Otherwise, over time, engine noise may increase, and cooling issues could arise. Regularly check the oil dipstick to ensure levels are within the normal range.
High-viscosity engine oil has the most direct impact on fuel efficiency. The engine requires more effort to pump the thicker oil, and the increased resistance may result in burning an extra half-liter of fuel per 100 kilometers. During cold starts, the slower formation of the oil film leads to insufficient lubrication, causing early wear. Another issue is elevated oil pressure—while it may sound protective, it actually increases the load on seals, raising the long-term risk of leaks. When choosing oil, consider the vehicle's age and climate. Older cars or those in hot climates may benefit from slightly higher viscosity to reduce noise, but for new cars, it's best to strictly follow the manual's specified viscosity (e.g., 0W-20) to maintain optimal performance. Use a viscometer or have a professional shop test the oil during changes.
