R30 is not highly refined leaves lots of striations I think they are called(verticle lines) on the skirt from the inclusions. Thats in a water cooled engine,air cooled don't seem to suffer from that problem. Castrol A747 is a better oil doesn't seem to be listed on the Castrol website. R30 was used in many gearboxes and think it was the 60's Hondas that would not finish the IOM TT without R30 in the gearbox
