This is the second time that i'm having a vitz 05 shape. here is brief outline of my experience of its fuel consumption
-- If your car is fully tuned it will give you between 16 to 19kmpl on high way depending on you driving speed. Ideal speed for good fuel average is between 80-90 kmph. These stats are without the use of ac, with ac deduct 2 kmpl approx
-- In city it will give you between 10 to 16 kmpl depending on your driving habits and traffic conditions. No traffic jams and keeping a light food on accelerator you'll get 15-16kmpl and a heavy foot with too many traffic jams or red lights and you'll get as low as 10-11kmpl. Again the use of ac not included.
-- I am of the opinion that fuel average within city varies from person to person so it can't be quoted as a fixed value
-- The fuel tank capacity is 42 litres but if you want to fill it to the brim than it might take in another 4-5 litres
-- Last fuel light on my car comes up when 7-8 litres are still in tank but this varies in every other car