i used ultimate, because its mostly avaliable.
bp now converted all their LRP tanks to ultimate, so now you povo bp station have ultimate.
i use ultimate because when running it in my old bike (2stoke) it ran better then optimax.
i do not notice any diference in the skyline between bp and shell.
the only difference anyone would notice is its detnation properties.
trust me, unless u get really shit fuel, you will not notice the performance difference, unless its 2 stroke. only way you can tell if its better or not, is if it pings or not.
you might get better ecconomy out of a certain fuel. maybe try stick to that fuel and reset your ecu. then see what your cosumption is like.