I must be doing something wrong then. The most I have seen of late 590 from a tank. I have a 1zz as well. For me there seems to be no difference between unleaded, PULP and 98 in terms of better mileage. The car does seem to accelarate better and have better power overall with 98. That is better pulling power, ie being able to pull 5th gear at 50km/h for example. The air filter panel in the car has now seen 12000k's It might be time for a clean and re oil.