2001 RAV-4, purchased 3/15/01 for approx. $18,000.
First re-fueling was on 3/20/01, and cost $1.379/gallon. Last refueling was on 2/20/05 and cost $1.759/gallon. Odometer reading at that time was 103972 miles.
2005 Prius, purchased 2/21/05 for approx. $22,000.
First re-fueling was on 2/27/05, and cost $1.879/gallon. Most recent refueling was on 4/17/08 and cost $3.399/gallon. Odometer reading at that time was 88461 miles.
*This log is a habit I inherited from my parents. I have a notebook with every visit to every gas station by date, odometer reading, trip reading, $/g, gallons purchased, total purchase price paid, location, and now for the Prius I include the displayed mpg (to compare it to my own calculations).