2005 taurus vs 1997 taurus

what hapened? i was getting good gas milage with my 1997 taurus 20mpg, my mpg display on my 2005 taurus states 17 mpg but i know i'm getting less. same size engine in both. what did Ford do so different. more air pollution devices? confused .

I know you have a 3.0 in both but, is one the DOHC 24V Duratec engine (200HP) and is the other the Vulcan engine(160HP plain jane engine). That would make a difference, don't forget the 05 is a little bigger than the 97.

also, you get much worse gas mileage with your AC on, have you been driving more with the AC on than you did in your '97?