What is the difference between Castrol Edge 0W30 and 0W40?

[Jeff]

Castrol Edge 0W30 and 0W40 mainly differ in high-temperature stability and viscosity. Difference in high-temperature stability: 5W40 has better high-temperature stability compared to 5W30. Difference in viscosity: 5W30 oil has slightly lower viscosity than 5W40 oil, making it more suitable for new cars and new engines. 5W40 oil has higher viscosity, which can enhance sealing and prevent oil burning. In practice, the difference between the two is minimal. Both 5W30 and 5W40 have a wide applicable temperature range and are all-season oils, providing good low-temperature start-up flowability and forming a thicker oil film at high temperatures to offer better engine protection.