Replying from the US...

I don't know what the differences are between US gasoline and European
gasoline (except we *never* call it petrol ;-)  ). Ours is 87 octane
standard, average of research and measured octane. There are "premium"
grades usually of 89 and 91 octane, and those cause the US model Prius to
misbehave and can turn on the emissions light. Detergency varies widely
here. Many areas use 10-15% blend of gasoline and ethanol or MTBE, sometimes
only in winter months, sometimes all year.

Here we see a big difference in fuel usage with the weather. Very cold
weather increases fuel usage as much as 20%. Wet snow on the roads can make
it even worse. Otherwise I've been getting just about the catalog
consumption in mild weather in my 2002 (first generation) model, at 7000 ft
elevation and lots of hills.

Mike

Also a reply from the US (Washington, DC climate). . .

Winter, I normally get around 45 mpg.

Spring/Fall is 55 mpg

Summer drops into the low 50s with air conditioner usage.

Well, there are different fuel economy test cycles in different
countries, as well as different fuel blends (European is lower in
sulfur than in the US, for example), that can account for some of the
differing fuel economy numbers.

You'll find more European owners at:
http://groups.yahoo.com/group/Prius-Europe/

My first tank of fuel in Australia gave me a consumption of 4.9 litres
per 100km using 98 Octane fuel with most of the driving at highway
speeds. The Prius has a lower fuel consumption rate in stop-start city
driving which is usually the figure quoted in advertising the Prius. In
Australia the official tested consumption rate is 4.4l/100k, which I
would expect from my vehicle if all my driving was in city traffic, but
I would be more inclined to accept 4.8l/100km at highway speeds (100km/h
- NOT Autobahn speeds!)

I got my Prius on Jan. 19 this year. That means I've mostly driven it
in the worst possible conditions as regards fuel economy - it's been
cold and I've had studded tires (as is legally required during winter
months in Sweden).

So far I've driven her somewhat more than 6000 kms, so I've barely
gone past the initial shakedown period. Currently she's running at
about 5 litres/100 kms. I'm expecting the consumption to be still
lower when she gets a few more miles under the hood (and after I've
changed to summer tires).

I drive mostly to/from work, which is 19 kms one way (according to the
monitor :-) in mixed conditions - first it's a highway and then it's
city traffic, i.e. stoplights and such.

I'll be happy to post further data when I've had her a bit longer. So
far I'll just say that it's the best car I've owned and worth every
penny!

I live in Europe (Belgium), and we've done 2000km's in our one month old
Prius now.

I've been doing some testing regarding the fuel consumption and have found
the following:
(Always 95 RON fuel)

City consumption: +- 5 liters/100km
Regional roads (70/90 km/h): 4.5 liters/100km
Constant 100km/h speed: 5 liters/100km
Constant 130km/h speed: 6 liters/100km
Constant 180km/h speed (seems to be the electronically limited top speed):
10 liters/100km.

All speeds are, of course, the ones indicated on the speedometer, and are
slightly higher than real speeds.

Overall average is 5.4 liters/100km now, which I'm very satisfied with, and
I'm sure no other current petrol driven car could ever come close to that.

The catalog consumption of 4.3 l/100km is the one measured by the EU
standards, and is always lower than real-life consumption, not only for
hybrid cars.

greets,
Emmanuel