I've just done a quick calculation averaged over 10 fills.
Ultimate 10.86
V Power 11.05
Vortex 10.8
These figures don't take into consideration seasonal variencies or type of usage, the fills were picked at random.
Based on this I would say that there is no real noticable difference between the three fuels as far as mileage goes.(For my vehicle). I can also say that I don't notice any difference in the bum dyno either. I also have had similar results for my missus's NA 2.0
Lib.

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MY05 STI