Fuel Mileage; oxygenated fuels

[LToy@aol.com]

Recently, someone posted a message on fuel mileage for a 4000 CSQ.
 (sorry--deleted the post)

When I had my '87, I typically saw 20 mpg mixed city/freeway driving.  My
daily commute was about 18 miles, about 6 of that city, the rest freeway.  On
extended freeway trips, I would see anywhere from 24-27, depending on speed,
traffic, and weather, although I must admit, I never really tracked
differences in speed!  I did notice that the more consistent I could keep my
speed, the better the mileage, regardless of average speed.  Weather was the
worst--I saw as little as 18 mpg at 60 mph average from Seattle to Portland
in a major rain storm.

FWIW, I recently completed a Seattle-SF Bay-Seattle circuit covering a couple
weeks (actually brought my car down for the QC event in Willows, CA, but it
got cancelled due to low turnout).  On 4 Mar, for the 805 miles
(door-to-door), averaging about 65 mpg, I averaged about 21.5 mpg.  This past
weekend, I took the car back, with a heavier load (+1 passenger), at
significantly higher average speed (BG!), and averaged 25 mpg!  Chevron 92
octane at all times.  I can only attribute that difference to the oxygenated
fuel required until the 1st of March.  btw, these are figures are calculated
from fuel purchases and the odometer, not from the trip computer (my 4000's
computer was never right--the 200 is quite close).    Any other experiences?