I just did a 3000 mi trip, 13.7 MPG @ 60-65 with a 22RE and automatic, 6160 lb weight.
14-15mpg sounds good for a V-6
Of course the simplest way to get 20 mpg is to lie about it, just like everybody else is doing who says they can get that MPG on a long trip.
I have gotten 21 mpg, but I was in Yellowstone NP driving 35-40 mph, but it was only one tank.