i get about 520ks to a tank, and it's not empty when i fill up. i use shell vpower. those are city k's, up/down hills etc.
r32 gtr, mods: mines ecu, steel wheel turbos, turbo back exhaust, 550cc injectors, greddy oil management, trust air pods. i have a powerfc ready to go in.
i reckon i could do better but my twin plate clutch means i have to give it some juice to move off the line.
edit: 520 kms / 51 litres used = 9.8l/100kms.