What is the difference between 5w30 and 5w20?

[DeOscar]

The difference between engine oils 5w20 and 5w30 mainly lies in their high-temperature viscosity. 5w20 has lower viscosity (between 5.6-9.3), which is relatively more fuel-efficient and provides a lighter driving feel; while 5W-30 has higher viscosity (between 9.3-12.5), which is relatively more fuel-consuming and makes the throttle feel heavier, but results in quieter engine noise. Below are the relevant explanations: 1. The meaning of 5w30 engine oil: The 5W in 5W-30 indicates the cold-start performance of the oil. Using oil with a lower number before the W makes it easier to start the engine in cold weather. The 30 in 5W-30 indicates the oil's viscosity characteristics at high temperatures. Higher viscosity oils (with higher values) may be more suitable for high-speed driving or heavy-load vehicles. 2. The meaning of W: The number before the W represents the oil's viscosity at low temperatures—the smaller the number, the higher the viscosity and the better the protection. The number after the W refers to the oil's viscosity grade at 100°C—the larger the number, the higher the viscosity.

[CorbinDella]

After driving for so many years, I think the most obvious difference between 5w30 and 5w20 is their viscosity. The 20-grade oil becomes thinner when the engine heats up, which reduces resistance and saves some fuel, making it particularly suitable for city driving in traffic jams. However, the 30-grade oil remains thicker at high temperatures, providing a more robust oil film at high engine speeds, offering better protection for long summer trips or frequent highway driving. Additionally, older engines with wear and tear are better suited for 30-grade oil, as it offers relatively better sealing. Newer cars may see more noticeable fuel savings with 20-grade oil, but never use 40-grade oil in winter, as it makes cold starts particularly difficult.

[StHarper]

Both 5W30 and 5W20 are all-season grades, where the '5' before the W indicates similar fluidity at -30°C. The real difference lies in the numbers that follow: 20-weight oil has a viscosity of 8-9cSt at engine operating temperature, while 30-weight oil is 10-12cSt. Lower viscosity oil reduces internal friction resistance, with actual tests showing the same car can save 0.5 liters of fuel per 100 kilometers. However, during aggressive driving when temperatures soar, 30-weight oil provides more stable oil film protection. Nowadays, many manufacturers use 20-weight oil as factory fill, but older turbocharged cars still require the protection of 30-weight. Choosing between them depends on driving habits and mileage—don't just focus on price.

[DeLucia]

Real experience using two types of oil: The 20-weight offers more responsive throttle, especially suitable for hybrid models, but engine noise becomes noticeably rougher when RPM exceeds 4000. The 30-weight shows clear advantages on long highway drives, particularly in summer temperatures above 35°C, maintaining more stable oil pressure. Once on a continuous mountain climb, using 30-weight oil resulted in 3°C lower coolant temperature on the same route. For frequent road trips, keeping 30-weight is recommended, while 20-weight suffices for daily commutes. However, always check the manual during oil changes - most German cars require 30-weight or higher.

[McLogan]

The low-temperature performance of these two is actually the same, with 5W indicating the same fluidity at -30°C. The core difference lies in the high-temperature viscosity at 100°C: 5W20 has a viscosity of 8.6-9.3 cSt, while 5W30 ranges from 9.3 to 12.5 cSt. The advantage of lower viscosity is fuel efficiency, which is why most new China VI vehicles come factory-filled with 20; higher viscosity is more suitable for high-temperature environments, especially in desert areas or under long-term heavy loads. A detail many overlook: long-term use of 20 may cause engine seal shrinkage, and switching back to 30 in older cars might actually solve oil burning issues. My experience suggests using 20 for cars under 6 years old and 30 for those over 6 years.

[StNatalie]

From a compositional perspective, 5W20 achieves a balance between low-temperature fluidity and high-temperature protection by adding more viscosity index improvers. 5W30 contains a higher proportion of base oil, exhibiting 20% stronger shear resistance. Practical observations reveal several key points: Japanese cars generally suit 20-weight oil better, while American pickup trucks are recommended to use 30-weight; in northern regions with -25°C winters, both grades show no difference in cold-start performance; for track use, 30-weight is mandatory. A common misconception is that lower winter numbers are always better - actually 5W offers optimal balance, whereas 0W contains more anti-wear additives that compromise long-term durability.