American Iron mag had this discussion some years ago. Lots of people got involved. Donnie from Heavy Duty Cycles, engineers, HD people. Anyway don't use auto oil for any length of time. Emergencies happen but MC oil is different from what was concluded like zinc that was mentioned.
An exception at the time was synthetics. My wife used synthetics in her 1200 and it ran noticeably cooler but it wasn't a scientific test. No tear down.
Oil is a more complex subject than I thought. There's lots of stuff in MC oil other than oil. This was back in 06,7,8 somewhere in there.