Mpg mph!

Unfortunately it's not just that simple, MPG depends on many factors: driver skill, "pedal feel", focus, route / terrain, etc. Over the 4 years I've had mine my milage has gone fom averaging mid 50's when I firts got it, to this summer consistantly around 70 / tank.
Last summer I was thrilled to be averaging mid 60's, so it's a process of continous learning / practice. KAIZEN baby !!! :rockon:

 

I can offer a "ballpark"...

On Saturday, I did a "down-and-back" from my home in Vernon Hills to my sister's in Champaign, IL. Traffic was about equal for both legs, as was weather/temperature.

For the outbound trip, I was just loafing along, with the cruise control set at 70 mph for about 70% of the trip. I averaged about 51.x mpg.

On the return leg, I wanted to get home. The cruise was set for 80 mph for about 60% of the trip and the rest of the time I was doing my best "Andretti" performance and I averaged 45 mpg.

Certainly not scientific, but shows about a 10% decrease by driving like an asshat.

 

I agree that it's hard to tell you the information that you are seeking...

I have just hit the 38,000 mile mark in mine, and even with the larger wheels on the Prius V, I have managed an average of 54.3 for my ownership... I live in the Chicago area, and commute 20 miles in each way daily to work, plus another 30-60 miles each of several days per week visiting some data centers in suburban areas. about 80% of my total driving is done in traffic. On the highway, I usually drive with traffic in the right lane, a few miles above the posted speeds. On city streets, like most, I am limited by the traffic, but most of my streets are urban, and therefore 30mph.

Of course, when I drive to friends houses, in the countryside, I get 65+ mpg for those trips as the 45-55 mph back roads are great for maximizing your mileage...

 

As others pointed out, there are too many variables. So what I do are a series of controlled benchmarks, ~10 miles each way, at different speeds on flat land to generate an mph vs MPG chart:


I also do hill climb tests:


These represent the best to expect from the vehicle within the limits of experimental error. Performance less than this suggests a different test protocol or possibly a problem with the vehicle. For example, temperature has an effect due largely to air density effects. Quality of fuel is also important. But these charts give a clue about what to expect.

Bob Wilson