I just took a road trip in my '05 ZX3/5sp. I traveled 1898 miles, and I consumed 53.4 gallons of fuel which averages out to 35.54mpg. Below is what I got for each leg of the trip:
Start (Sierra Village CA): 26142 miles - Full Tank
Redding CA: 26421 - 279 miles - 7.9 gallons - 35.3mpg
Bend OR: 26697 - 276 miles - 7.61 gallons - 36.27mpg
Yakima WA: 26933 - 236 miles - 6.77 gallons - 34.86mpg
Yakima WA (after Mt. St. Helens Trip): 27217 - 284 miles - 7.91 gallons - 35.9mpg
Bend OR: 27472 - 255 miles - 7.63 gallons - 33.42mpg
Redding CA: 27747 - 275 miles - 6.97 gallons - 39.45mpg
End (Twain Harte CA): 28040 - 293 miles - 8.61 gallons - 34.03mpg
I filled it up with 89 octane every time, I find the car runs better on this and that the computer doesn't have to change the timing to prevent ping as often (10:1 compression and all). Four of the fill-ups were at Chevron, two at an AM/PM, and the other start and finish fill-ups were at local gas stations that are not part of a chain. For speeds, all of the California driving was mostly 75mph, with some 80mph mixed in, and a good stretch of 55mph. Oregon limits are all 55mph, but where I was going was out in the boonies so I generally went 65 (as did everybody else). Washington was mostly 65mph. Some of the areas were fairly mountainous, but going down one side of the mountain generally makes up for going up the first side. The trip between Bend, OR. and Redding, CA. is great for gas milage as there is a very long stretch that is perfectly straight and flat for about 50 miles with a 55mph limit so the car just sips fuel.
Overall the car did great. I did a fair bit of city driving in Washington, along with about 24 miles of rally on gravel (very fun and the car did very well for being mostly stock). But it didn't require much WOT driving.