my dad works at the shell oil refinery in sydney where they produce the stuff.shell in nsw supplies bp and bp supplies shell in queensland as they dont have their own refineries in each state.
BP however do put some extra additives in their fuel that they get from shell in nsw that magicically clean your engine and make your car like a race car LOL.
but with shell, mobil, bp they are pretty much the same in terms of performance and economy id say vortex is just as good but has been known to have some bad batches of fuel hope this helps