What are the effects of high oil viscosity on the engine?

[DelHaven]

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.

[VincentLynn]

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.

[DelSienna]

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.

[McSavannah]

If the engine oil is too thick, the engine will not run smoothly. I feel like the car is carrying a heavy load, with slow acceleration and increased fuel consumption, especially during frequent short-distance starts in the city, resulting in poor lubrication and increased wear on parts. High temperatures may also lead to poor heat dissipation or noise. Stick to the specified viscosity to avoid these issues and pay more attention to the recommendations in the car manual.

[DeWeston]

Using high-viscosity engine oil increases internal friction in the engine, which is equivalent to adding extra weight to the vehicle. This will inevitably lead to higher fuel consumption, costing more per kilometer on long-distance drives. In low-temperature environments, starting becomes more difficult as the thick oil flows poorly, potentially damaging bearings or cylinder walls and shortening component lifespan, resulting in higher maintenance costs. Although high-viscosity oil offers some cushioning benefits during frequent acceleration, the overall drawbacks outweigh the advantages. I once tested viscosity when changing oil myself, and the engine vibration noticeably increased. I strongly advise against exceeding the manufacturer's recommended viscosity grade, such as SAE 10W-40, and maintaining a moderate viscosity to protect engine health.

[Lucian]

High-viscosity engine oil makes the engine work harder during operation, resulting in slower power output. Fuel consumption increases significantly, costing about 50 yuan more per month on gas. Cold-start issues become more pronounced, as the slow oil flow leads to insufficient lubrication, exacerbating wear and affecting crankshaft lifespan. Although the thick oil film provides temporary protection at high speeds, daily driving efficiency is generally lower and may even cause overheating. Choose oil according to the manufacturer's specifications, such as 5W-30 or 10W-30, to balance lubrication and efficiency. Remember to change the oil regularly and monitor its quality to prevent carbon buildup.