larger tyrer diameter V's fuel use

Hi all,
I have an 02 dx d22 t/d. They originally came out with a tyre size of 205/80 r16. I currently run 225/75 r16, the biggest the standard wheel will take. I know the str came out with bigger wheels and tyres and both specs have the same gearing. My question is, when any of you increased your tyre size did you notice an increase or decrease in fuel consumption and by how much? I understand tread pattern plays apart in fuel consumption too. I am trying to find out ways to "mechanically" improve my fuel consumption and see if it is worth paying the extra money for larger tyres. I currently get between 500-600km per tank.

Mate this type of question has been answerd in all the fuel economy threads in one form or another, maybe try looking through some of those before starting another thread.