Does anybody really have a strong opinion on the synthetic oils? I buddy of mine wanted to put Amsoil in all his cars so we registered for an Amsoil dealership. He put it in an 03 H2 and a brand new maxima and says its great but I haven't done it yet. I've heard that switching to synthetic on older high milage vehicles makes them more prone to leaks and that its too late to justify the expense of the synthetic over normal.......