0W-30 is the best oil for your car, assuming you live in Europe and you won't be circuit racing it.
Both Honda and Castrol recommend 0W-30. A thicker oil at temperature (the 30 bit) may cost you some power and economy. A thicker oil when cold (the 0 bit) may cause more engine wear at startup. Higher numbers = thicker.
Castrol 0W-30 is a very good example of that oil, though there may be better.
And where does it state that? Because I am looking at it and I can't see it advising Semi SyntheticThe manual states 10-40W Semi Synthetic on the CTRs, there must be a reason for this, when other manufacters use fully synthetic in their cars. It can't be due to cost cutting but the way the engine has been designed? Semi synthetic oil is thicker than fully synthetic!