Most are to thick and as NFRAP2 said most high performance motorcycles have wet clutches, our cars don't. So we can use better oil than motorcycle oil, ones with lots of Moly and other friction modifiers. They took most of the zinc and phos out of auto oil because they(the feds here in the USA) wanted the cats to last longer and when you remove most of the the zinc and phos out of the oil they do.

ROD