plenty of other oil sitting around. I have some synthetic Spectrol 10-30 from my motorcycle days or some other conventional 10-30 or 10-40 oil. Should I stick with the manual and only use the 20-50?

 

I use 10w40 penzoil!!!! never a problem

 

Don't use Synthetic or you will tear up your clutch & burn it out...synthetic is GREAT oil, just not in older friction needed machines, that is what these Chinese machines are & require some friction that synthetic does not have. I would use 10w40 Castrol GTX.