Shell Premuim is very good octane!!I run premium as the ethanol in lower quality gasolines has ethanol in it, which will eventually.dry rot and dissolve the rubber components that come into contact with fuel.or fuel vapour such as the grommets on the fuel tank, primer seals, fuel pump seals, carb components. If you want high performance run race leave octane stuff. You want longevity of motor, run as low of a quality as you can that has no ethanol unless you want tonreplace 13$ grommets every few years as well as numerous other components. Just my 2 cents. I run shell premuim, the nitrogen enriched stuff with no ethanol.