Years ago when synthetic oil first hit the market, I was living in England and was using the European version of Castrol dino oil, and swore by it. Then I heard that Castrol had developed a synthetic oil based on dino oil, and then they went to court and had it declared a synthetic oil. I swore off Castrol at that point because I felt that their synthetic was called synthetic due to a legal decree by the courts. But now after reading several pages of online oil analysis, I find that Castrol synthetic is just as good as any other synthetic and I will probably start using it again.