octanes...87, 89, 93. There are even higher octanes at race tracks, and a few other places (that i don't know of). If you have a new z28, it says it wants 91, funny $#!T huh? to get 91, you fill half w/89, and half w/93, if ya wanna be cheap
I don't think so... I believe that all chips make the most performance difference from the optimization from the better fuel. I haven't seen one that doesn't recommend premium. But the way I see it... It is really only a buck or two more per tank.