I usualy get about 300-310 miles on a full tank before E light comes on, which leaves 2-2.5gallons remaining, so that's about 27mpg. Which is fantastic for an automatic. going on fumes I'd probaly hit 345-350ish. I mostly do semi-highway driving, but it's defentaly not without alot of stop and go stuff too.
I have a 2000ES 1.8L and have a CAI and used denzo iridium plugs, other than that it's bone stock.