For the money, the best engine oil for a high-revving 660cc engine is a true synthetic like Mobil 1. The reason I advocate a synthetic is quite simple: a true synthetic is engineered from the start to work in high-stress, high-temperature situations that leave other oils breaking down.
A true synthetic is blended so that it uses complete carbon chains to do its work. Not only are the chains engineered to slip easily past one another, but they are also built to handle the heat because they are full carbon rings.
A standard mineral-based oil like a good 5W-30 works up to a point. It is thin and has good short-term wear characteristics but you will find that after a relative short time, depending on the service your 660 is in, the oil will start to break down, leaving you with little more than a black mess in the oil sump.
A synthetic, on the other hand, easily stands up to the heat and wear high-revving and temperatures bring.
I know that where you live 5 quarts of Mobil 1 may be expensive. It is, after all, a premium commodity. That said, because you choose that particular synthetic, it means that you care about your engine and vehicle and want to give it the best chance you can.