I can't say I've noticed any performance difference between the two (my bike is still stock). The manual says to run "Unleaded" and the dealer told me to put Premium (except Optimax

However, I was just looking over the numbers this morning (I've been keeping track of my fuel fills) and was surprised to discover that despite being up to 10c/L dearer, it's actually cheaper ($/km) for me to run Premium - by up to 0.5 c/km. Now that doesn't sound very much

So now I don't feel so bad about paying that extra $2 odd for my tank of fuel!
Cheers,
Russell.