Yes, It's a 3-Litre (See link
Fuel Economy of the 2000 Dodge Caravan/Grand Caravan 2WD) and the ScanGauge was adjusted at the last fill up (EDIT: But did I do it properly?) Almost 6 gallons have been used so far. The van tends to get better economy if at a lower elevation; We're located rather high. (EDIT: Is that true?)
Also, The rear passenger seats were removed and the AC belt isn't connected.
Edit: The engine says it's a Chrysler.
EDIT: I'm wondering if it's true that the van gets better economy at a lower elevation and it's not just the fact that it's on a 100+ mile trip.