We were on wheels totaly 13 days and approx 5000km. Average mpg was a surprise - 12,3L/100km. Gasoline price in Norway was about 2€ (EUR) per liter.
Mods for trip:
* Installed a 600w inverter under the passanger seat. Had to install fuse and cables from battary to inverter.
* Removed middle row middle seat. So the kids can get in and out more easily.
Photo for forum:

GPS tracklog and some pics here. (It is written in Estonian but hopefully Google will translate it quite well.)