Peter, l am no expert on oils but l have used Morris running in oil for some years in both Vincent and BMW engines. lt was explained to me some years ago that running in oil contains very few additives, is of a low viscosity and therefore promotes bedding in of rings and carbon formation where required. l drain it after 500 miles, flush with flushing oil and then install regular oil which in my case is Morris Golden film 20/50. Not had any grief with it and have some very sweet running motors. Just my experience, others may have a different take on it. Mind how you go............