Sinto uses highly refined Group III, mineral base oil. It is not a true synthetic and not the same thing as Amsoil, which is an engineered, Group IV, Ester base product. I hope it works for you, but if it does not, you still won't know if a true synthetic oil will give you the releaf that you're looking for.
It is a shame that the industry is allowed to play these word games, selling mineral oil as 'Synthetic' when, in fact, it is not. Europe does not allow this slight of hand marketing. So, in North America, it falls to the customer to sort things out. Most never know what they are getting.