just stick with 85-87 octane. most engines are made for cheap fuel, never noticed any preignition in any small engines running 87.

i've run penzoil,lawn boy,havoline,echo,redline,amsoil.
reg. oil
i run 32/1 ,break-in.
40/1 after.
same results, after several gallons of penzoil the engine is really clean. lawn boy seemed to carbon up a bit, and spit out the exhaust more than others.

using 100/1 amsoil sabre on my DA-50 for 4 gals now,havent had an issue.
mostly just stick with what the manufacturer says and you'll be ok.