I have kept records on the Subie mileage since I did the conversion in Dec.
of '04.  Of course there are a lot of variables - altitude, weight, driving
speed, wind speed and direction, in town vs. highway, etc.  The best mileage
is at altitude - especially driving on winding mountain roads.  Intuitively,
that doesn't make sense, but I get 22 to 23 mpg in those conditions.  In the
flatlands of Kansas and Oklahoma, I average 17 to 18 mpg.  In particularly
strong headwind conditions I've gone as low as 13-14 mpg.  My average
mileage over the last two months, which includes city and highway driving,
is 19 mpg and that is mostly in New Mexico and Arizona.  All in all I am
happy with the mileage - and of course YMMV.

Maggie
'85 Subaru-Westy "Anne Bonney"