Thanks for the plug Sam. When I posted this calculator a few months
ago, I got about a dozen replies saying that it was actually pretty
accurate. This is a slightly revised version based on comments that
I received and Sam's study of mileage vs temperature. (added #7 & 8,
revised values on #3)

To estimate what your average mileage might be, start with 45 mpg and
make the following eight ± adjustments:

1) Percent of trips (from cold start) less than ~10 minutes:
0%:+2, 33%:+0, 66%:-4, 100%:-8 (consider an EV)

2) Percent of time AC or defroster on:
0%:+1, 33%:+0, 66%:-1, 100%:-3

3) Outside temperature:
below 10F:-9,10-30F:-6, 30-50F:-3, above 50F:+0

4) Percent of time spent in crawling stop'n'go traffic:
0%:+0, 33%:+1, 66%:+2, 100%:+4(consider moving)

5) Percent of time using techniques to maximize Prius mileage (i.e.
gradual start on electric, then quick acceleration on gas, then foot
off gas pedal when cruise speed obtained):
0%:+0, 33%:+1, 66%:+2, 100%:+4

6) Do you drive very aggressively? (i.e. jack rabbit starts, speed >>
average traffic speed):
No:+0, Yes:-3

7) Are your tires under inflated?: (less than 35psi front, 33psi rear)
No:+0, Yes:-2

8) How many adult equivalents does your Prius carry on average?:
1 or 2:+0, 3 or 4:-1, 5 or more:-2

Add or subtract these ±values from 45 mpg to get an idea of what
mileage you might get. Feel free to interpolate. Remember: Your
Mileage May Vary (YMMV).

I have based these factors on my 3300 miles in a Prius, plus the
polls, studies, and messages in this and the Yahoo site. Comments or
suggestions are most welcome.

Chuck Gibson