Does Castrol not have 0w20 engine oil?

[DeArthur]

Castrol does have 0w20 engine oil and it is fully synthetic. The base oil quality of 0w series is generally good. It is quite suitable for high-precision engines in Japanese, American, and Korean vehicles that don't require high high-temperature shear resistance. The downside of 0W-20 grade oil is that it's relatively thin and not suitable for all vehicles. If the kinematic viscosity of this grade's oil is too low, it may lead to oil burning. It has excellent low-temperature performance, capable of smooth startup even at -35°C. Fully synthetic oil has a higher viscosity index compared to conventional mineral oil. With the same oil film requirements, synthetic oil can achieve the target with lower viscosity, whereas mineral oil requires relatively thicker viscosity. Moreover, fully synthetic oil shows minimal viscosity changes with temperature variations, thus maintaining appropriate viscosity in both high and low temperatures to provide proper engine protection. Under the same working conditions, fully synthetic oil also lasts much longer than mineral oil, which is why some oils claim to have a 10,000 km change interval.