My driving: 85% hwy, 15% taking the kids to school and otherwise tootling around this small town.
I've had no trouble maintaining an avg over 40 mpg starting with my 2nd full tank.
2.5-week total: 48.11 gallons, covering 1993.7 miles:
41.44 mpg.
I've hit 350 miles twice in 8 tanks, but the other times, I filled up quite early on. [On two occasions, I was resetting the ScanGaugeII for the fillup accuracy. My readouts are now much more accurate. Before I made the adjustments, it looked like I was getting over 50 mpg routinely. Ah well.]
I have a big trip (600+ miles) in a few weeks where I'll get a chance to use up most of a tank on one highway run, so it'll be interesting to see how that plays out. And then I get to try it again, in the reverse direction, a week later.
I drive slower than allowed, averaging about 60 mph, and I have begun drafting from a safe distance (100+ feet?) for a few little boosts. I also avoid the A/C when possible. Lately, that's been impossible, so I keep it to the lowest setting.