Which oil is thicker, 5W20 or 5W30?

5W30 engine oil is more viscous than 5W20 engine oil. The high-temperature kinematic viscosity range of 5W20 is 5.6-9.3 cSt, which is suitable for new cars or precision engines, and can improve fuel economy by about 3%-5%, making it especially suitable for urban commuting and cold regions. The high-temperature viscosity of 5W30 reaches 9.3-12.5 cSt, with higher oil film strength, providing more comprehensive protection for turbocharged models or older engines in high-temperature environments, reducing noise by 1-2 decibels, but increasing fuel consumption slightly by 1%-2%. 5W20 is recommended for new cars or gentle driving, while 5W30 is recommended for high-mileage cars, hot regions, or aggressive driving. Ultimately, the vehicle manual's recommendations should prevail.