Ive found Shell's V-Power to have pretty good fuel efficiency after the first 2 tanks or so run through. Im actually using the new V-Power Racing (100Octane 5% Ethanol) Nice smoother power delivery, ive tried the BP Ultimate and they are definantly similar but car seems smother with Shell's Petrols.

Fuel efficiency is again similar when comparing 98's but with the V-Power Racing if im driving conservitivly i can get around 520kms out of a tank. (Stock VTi-R) With occaisonal trips into the VTEC Range.