I have a 1.4 petrol 54 plate
Ibiza, I put £20 in and maybe get 150 miles before the light comes on again.
Obviously when the petrol light comes on it can have more in it that the computer says but I don't feel i get good MPG with it.
Had it major serviced in January too because it hit the 80k mark and the guy I bought it off didn't service it for 2-3 years.