I have a 2004 4WD V-6 X. I get around 21.5 mpg on the highway and about 17-18 in the city. I drive at or right above the speed limit. I was really anal about breaking the engine in when I bought my X. Maybe that's why I'm getting such good mileage...Does anyone have a thought on this? I also have a K&N filter and I keep my tires at 42 psi.