I have a 2008 Highlander, V6, 2WD.
For city driving I average 18-19mpg. I get to 21-25mpg, if I use the Pump & Glide technique (pump the gas to traffic speed then put the gear into neutral until the car is too slow for traffic, then pump again) and traffic is good. Believe it or not, putting the gear in neutral goes a looong way at improving mileage.
For highway mileage, I average 23mpg going at 85-90mph. 25-26mpg at 75mph, and when I drop down to 55 or 60mph, I get an amazing 34mpg. You really start to see a difference below 60mph. For me, I go about 60mph around the local freeways, and on long trips, I go about 85mph.
One time, I was going about 60mph, using the pump & glide technique along with some drafting behind a semi and I was able to get 54mpg for a 7 mile stretch. If you are really interested in improving your mileage, do a search for "hypermiling". Here is a great article.
http://money.cnn.com/2006/05/01/Auto..._mpg/index.htm
Techniques
http://www.cleanmpg.com/forums/showthread.php?t=1510
I hope this helps.