I have a 2002 Xterra S/C XE.
It runs great except for the horrible gas mileage I am currently suffering from.
Now I know the X's don't get that great of mileage, but its getting ridiculous!
I had half a tank of gas and drove from Denver to Greeley and when I just got there, the first red light my gas light turned on.

I checked plugs, they are clean. I checked timing, idles at 10 degrees. When I bought it, about 3-4 weeks later the check engine light came on due to a faulty o2 sensor, replaced it, cleared codes. I checked codes again, nothing.

What else could I check for? Whats common problem of why Xterra's suffer bad gas mileage?

Thanks
Alex