I myself have not noiced the fuel economy difference at all... Before doing any engine mods and after the engine had a few 1000kms on it I would get 340km out and fill up with about 14L, I am still getting that with Dynojet jet kit 98 main needle, Areap Full QC and snorkell out. A few fills ago I got 350km and I only filled with 13.5L... I guess it depends on the right hand, though I have been going harder with the mods