My "new" 2007 Sport Edition does the same thing. I have just started searching for info on this symptom and I found one thread with similar comments so my guess is that this is normal. I hope someone who knows what is actually going on with this will post here though.
Pat
Is this mainly highway driving or city? Also, do you feel there is anything special you are doing here? I am getting ready to purchase a 4-Runner and the V8 sticker shows something like 14 & 17 for mpg. How do you think you are achieving better than this? Usually it is the other way around...