Is O'Donnell 20% Racing fuel ok for using in a hpi type ss and super nitro?

Yep, thats good to use for the type SS and super nitro as well. I used duratrax red alert 10%, blue thunder 10% and currently powermaster 20%, they all worked fine for my type SS too. I even tried SIG Heli mix 20% (about 5 tanks) and it also worked fine with lots of smoke. For as long as you tune your engine on the rich side, you'll be doing OK.

Enjoy your SS !