Synthetic oil really isn't an issue for motorcycles. They make synthetic MC oil. The problem with clutches lies in the friction modifiers they use in auto oil. I've used Mobil1 synthetic in my bike for several years with no problems. Now this is a pretty heavily modified ZRX with 140hp at the rear wheel. I'm still on the stock clutch at 24,000 miles. I'm not trying to preach to any of you, but for a few cents more a few times a year, why risk using auto oil? I don't get it.