Try Meguiar's Cleaner/Wax. It will clean the black stuff off and leave a wax that will make it easier to clean next time. What you are experiencing with your new G-38 is very normal during the break in process. The reason a synthetic oil like Amsoil will show less black residue is because it slows the break in process way down. As soon as the break in period is over you should not have the black stuff and then you can switch to synthetic. In the mean time just try to keep it clean with one of the methods suggested.

Good luck,
Ken