I found a site to help you track your MPG, and compare with other Foci, as well as other vehicles.
Here is my Focus page on Fuelly
Zetec Crew #240
NEW2ME 01 ZX3 Green, 2.0 5Spd (DOA-Work in progress)
SOLD - 01 ZX3 Pitch Black, 2.0 5pd (32MPG)