short trips
We bought the car in June, drove 600km, and then headed off to the Yukon for the summer. Three bikes on a rack on top. Lots of highway driving, lots of exceeding the posted limit. Worst mileage/kilometrage was 10.2L/100km. Best 5.5L/100km. Average over 11,000km was 7.0L/100km. Recently I filled up and drove 70km over the hilly Malahat Drive north of Victoria. When I pulled into the driveway it indicated 4.2L/100km. This is the EPA/Toyota advertised kilometrage for highway driving for the 2004 Prius.
The car was purchased for my wife to use for work. She is a community health care nurse and she has a small, urban area for a district. This means that she drives a short distance from the office in the morning, visits a client for approx. 45 minutes, then drives a couple of blocks, visits a client for 45 minutes, and so on all day long.
She has difficulty obtaining under 8L/100km. It is possible that she is driving the vehicle all wrong

but more probably it is the nature of her work.
I'm sure she would like to achieve the EPA/Toyota advertised in-town rating of 4L/100km but she isn't so she has to be satisfied that in the course of her work she now fills up every three weeks instead of every week with her previous vehicle, a '91 Toyota PU with the 22RE 4 cyl engine. And since she is paid CDN$0.44 a kilometre she's offsetting the cost of gas, maintainence, insurance and loan costs. And she is driving a really cool car that everyone in the office wants to know more about and at least one has ordered a Prius. 8)