I've been a Prius owner for 7 years and I compiled all my data into a report on the performance and maintenance. The report is at http://enerjazz.com/prius/PriusAt7.pdf Here's one chart:
70 to 80 deg F seems ideal. I see you have 3 Prii. Is the data from a single Prius or a combination of the 3?
I like this one the best: It looks like the Prius came out at the right time (right before gas price started to skyrocket).
Yes, I like the way the gas price has tracked my mileage. And my data is 5.5 years in the 2004 and 1.5 years in the 2007. It's all my driving. At some point I'll show the comparison of the 2004 data with me driving vs my daughter. It's quite a drop, but she is running very short trips to/from school, where I have a long steady commute.