Don't fret using regular oil. The synthetic is better, but you could probably put vegetable oil in it and have it run ok.
Ok, probably not really Crisco, but you get the idea.
I know guys that is all they use, the cheap stuff, bikes run just fine.
I use the shell rotella T diesel oil. I guess it is a semi-synthetic, but have had no problems in many miles in all extremes of temp, even with the big bore.
