that's exactly what I would expect. If it starts falling a few mpgs w/o any other change in driving habits, thats a good indication that there are air:fuel mixture problems, maybe not even triggering a check engine light or restricted performance code, but would benefit from a thorough air/vacuum line look-see. enjoy your 03!

 

I had my Jaguars run through the Terra clean
Both more than 75k miles
Stunning improvement to the consumption economy

 

I have a obd2 dongle by Automaticlabs. It records driving style and MPG and will interface and when I am really **** it will sync with OBD Fusion and give me real time readouts of various settings and save them to a file on Dropbox. So far this year I am averaging 23 mpg but much of that is on freeways. In town only I get 9-14. It's only $100 and often on sale for $80. You can see exactly what your temperature and oil pressure are running

 

My 2001 XK8 gets an average of 16.9 MPG in sport mode. If I take longer trips, ie. 200-300 miles I get around 19.