royal purple is different from most synthetic motor oils because it uses a high concentration of microscopic calcium particles that fill in the gaps so to speak in the cylinder wall which provides better piston ring sealing and compression and therefor increases the HP of the engine. There are downsides to this high concentration however, namely, if used for extended service periods the metal particles can acutaly start to accumulate in the oil galley passages which eventualy leads to restricted flow/clogged passageways.
so if you must use royal purple, even though it's marketed twoard exteneded services periods, I would suggest nothing longer than 5K, or mabye even less.
