It depends on what is available to you. Some of the wisest moped veterans will tell you marine outboard stuff is fine, or whatever you can find. Others will tell you if you use anything less than motul your a loser. I buy the synthetic stuff I can get around here, its called amsoil saber and it seems to do the job just fine, although it is a tad pricey. Anything sae certified or whatever it is will be fine.