Just rolled in from a long day's tour of the SE corner of the Cascade range
in my 84 'topless' camper with the inline four 1.8l rabbit motor.
  I've not done a highway trip since early spring, but I have done  eminence
and a few minor mods.  I changed the plugs (they had about 30k miles on em
and were all perfect color range, but they'd eroded away to have about 40
thou. gaps)  I also replaced my tranny fluid with new Redline synthetic,
added a 'chin-spoiler' made from ABS garden edging, emptied the water tank
(unless I am planning on camping) and cleaned or changed all the filters.
I've been getting 24+ mpg around "town" if you call my local "town" (I do)
though it is not city driving, by any means.
  I went via interstate (84)to Portland and almost up (I-5) to Olympia,
headed to a bike race...But it was raining hard and even when it's dry, a
bike race has enough suffering, so I bagged it.  I filled up and headed
east, between Mt Adams and Mt. Rainer on some small paved forest road I'd
never traveled before..Then across White Pass to Yakima ("The Palm Springs
of Washington" according to their sign)  I got in a nice warm bike workout
behind Naches, Wa. then headed for home across Satus Pass,  back into the
Gorge.  On the one full tank I got during the trip, mostly climbing
switchbacks and a little regular highway, I got my all time best so far fuel
economy of 27.87mpg.  The motor seemed quite happy, kinda sounds like a
Mexican Taxi or a Honda Crotch-rocket motorcycle, with it's little
high-winding inline four and it's magnaflow SS muffler..  It will be
interesting to see what the rest of the trip mpg comes out.
  Exactly what a bus is supposed to do perfectly....it did.
  Don Hanson
 (I am typing this with my toes, legs and everything else crossed...hoping I
didn't jinx myself by saying how good it is..)