It is a very good oil. I checked the Castrol website. The number

really impressive and better than most 10W-30 and 10W40 oils at high temp. Although it is not certified by API, the oil is tested and approved by Mercede Benz and other European car makers. I guess it will be fine using it to replace 5W20 and 5W30 oils and outperform them. This oil meets the SH standard, which is the best gasoline engine oil standard ever in terms of protecting the engine parts. And the price is very reasonable too, actually the same as the other Castrol Syntec oils. It is a very good bargain. Thanks for the info.